This place can be daunting as it has a tremendous amount of data.
And, its index system is archaic; especially the legal portions
which I swear were deliberately made confusing to frustrate the
lay person.  It takes time to get the hang of the place but the staff
is usually helpful, especially if you have done some preparation
and have specific questions.  However, like many archives, it can
treat genealogists with (sometimes deservedly) less concern than
historians.  Make very careful notes as to what you've done or
you'll end up duplicating your work.

Some of their records are held 'off site' and require a couple of
days notice.  Copies of items are cheap but again take time
(however, they can be mailed to you).

Of course, there are researchers who specialize in these records.
They are expensive but sometimes necessary.  With them, it's best
to know and state exactly what you want as they love sending you
(and charging for) the easy stuff you likely already have.  I may
be able to guide you so give me a call.

I recommend you invest in a copy of HMSO's Tracing your
Scottish Ancestors.  It gives a brief description of the genealogy
records available in the SRO and how to access them.

 This is the book's index: 
   Accident Records
   Accountant of Court
   Acta Dominorum Concilii (Deeds)
   Acts and Decreets Register
   Adherence (marriage)
   Adjournal books (criminal court)
   Adjudications Register
   Admiralty Court
   Adoptions
   Advocate's Records
   Affiliation Orders (court records)
   Agric and Fisheries Dept
   Aliment Cases (illegitimate b.'s)
   Anatomy Schools and Insp
   Apprentices
   Apprisings Register (debt)
   Architects
   Argyll Justiciary Court
   Army Records (mainly at PRO Kew, Ldn)
   Art, Edinburgh School of
   Artists
   Asylums
   Bachelors
   Bailiary
   Bankrupts
   Banns of Marriage
   Baptisms
   Barony Courts
   Baxters (bakers)
   Beneficium Inventarii (heirs)
   Bill Chamber
   Birth / Bapt Records
   Burgesses
   Burgh Registry of Sasines (deeds)
   Burgh Courts, etc
   Burials
   Business Records
   Calenders
   Carters
   Cartularies (grants)
   Cathecists
   Catholic Apostolic Church
   Cemetary Records  (many are indexed by local groups)
   Census Records  (a few earlier ones survive; usually with OPR's)
         1841    7 June
         1851   31 Mar  (many areas are indexed by local groups)
         1861    8 Apr
         1871    3 Apr
         1881    4 Apr  (indexed & available on Mormon's CD)
         1891    5 Apr  (indexed by SRO)
   Cess (land tax)
   Chancery (court)
   Charitable Foundations
   Charters
   Chemists
   Church of Scotland
   Clare Constat (inheritance)
   Clergymen  (see Fasti Ecclesiae Scoticanae book)
   Coal Companies
   Commissariot Courts (mainly re marriage & legitimacy)
          Court Locations
   Commissions
   Confirmations Calendar
   Congregational Church
   Consistorial Records (commissariot)
   Cordeners (shoemakers)
   Corrections Register
   Cottars
   Council and Session Books (deeds)
   Councillors, Burgh
   County Records
   Court of Session
   Cousins and Cousin German
   Craft Guilds and Incorporations
   Craftsmen
   Creditors
   Criminals
   Crofters and Cottars Colonization Board
   Crown Estates
   Curators
   Customs Accounts
   Customs and Excise
   Dean Orphanage
   Death and Burial Records
   Death Duties
   Debtors
   Deeds Register (Deeds office is very expensive; few owned land)
   Defence Ministry
   Defuncts (personal estates)
   Dentists
   Destitution Boards (lists of poor agricultural workers)
   Dick Trust (teachers)
   Diligence
   Dioceses
   Directories (City)
           McG's in the Glasgow Dir's; 1787-
1886
   Disabled
   Dispositions and Settlements
   District Council
   Divinity Students
   Divorce Cases
   Doctors Register
   Dyers
   Edinburgh Castle Governors
   Edinburgh Cemetary Co.
   Edinburgh School of Art
   Education
   Elders of Kirk
   Electoral Registers
   Emigrants
   Entail (inheritance)
   Episcopal Church
   Estate Duty
   Estate Land Papers
   Exchequer (taxes)
   Exchequer Court
   Excise Officers
   Executry Records
   Factors Loco Tutoris (minors)
   Farmers
   Fasti  (1560-1929) (see Clergymen)
   Fatal Accidents (industrial inquests after 1895)
   Fishery Board
   Fleshers
   Forfeited Estate Papers
   Fornication
   Franchise Courts (rentals)
   Free Church
   Freeholders Rolls (landowners)
   Friendly Societies
   Gardeners
   Genealogies, published
   General Register of Sasines (deeds; see Sasines)
   Gifts and Deposits
   Goldsmiths
   Government Officials
   Gravestones
   Great Seal Register
   Gretna Green Marriages
   Guthie's Schools
   Hammermen
   Health Ministry
   Hearth Tax
   Heirs
   Heriot's School
   Heritable Property
   Heritors Records
   Herring Fishermen
   Highland and Island Emigration Society
   Highland Destitution Records
   Highlands and Islands People
   Highlands and Islands Royal Comm'n
   Home and Health Dept
   Hornings (debtors)
   Hospital Records
   Householders
   IRS (death duty)
   Illegitimacy
   Income tax
   Inheritance
   Inhibitions Register (wills) These and Inventories are self-serve.
   Inland Revenue
   Inn-keepers
   Inquest
   Inquisitionum Retornatarum Abbrev (heirs)
   Ireland
   Insane
   International Genealogical Index (IGI)
   Intestacy (wills)
   Inventories of Heirs
   Inventories of Moveable Estates
   Inventories of Property of Crown Debtors
   Irregular Marriages (Without clergy; legal before 1940, but
         discouraged)
   Judges
   Justicial Rentals
   Jury Court
   Justice of Peace Courts
   Justiciary High Court
   Kirk Sessions (Church notes; a great source)
   Land Court
   Landowners
   Land Tax
   Lawyers
   Legalees (language)
   Licensing Courts
   Lieutenants of Counties
   Linen Industry
   Litigants
   Litsters (dyers)
   Local Courts
   Local Gov't Elections
   Lodgers
   Lunacy Commissioners
   Mc / Mac
   Manufacturer's Board
   Maps and Plans
   Marriage Contracts
   Marriage Records
   Masons
   Medical Practitioners
   Mental Welfare Comm'n
   Merchant Seamen
   Merchants
   Methodist Church
   Midwives Roll
   Migrants
   Militia Records
   Miners
   Minute Books (deeds)
   Missionaries
   Monumental Inscriptions (tomb-stones)
   Mortcloths
   Movable Property
   MP's
   Ministers
   Muster Rolls
   Names Changes
   National Coal Board
   Naval Records
   Newspapers
   Non-conformist Churches
   Notarial Protocol books
   Nullity of Marriage
   Nurses Registry
   Obituaries
   OPR's (see parish registers, old)
   Ordnance Survey Maps
   Original Secession Church Ministers
   Orphans
   Pardons
   Parish Councils
   Parish Registers, Old (OPR's)
          Numbers
   Parochial Boards
   Particular Register of  Sasines (see Sasines)
   Passports
   Patronymics
   Paupers
   Pensioners
   Phone Books (few people had phones before 1950)
   Physicians
   Plans
   Police Books (a great source)
   Poll Books
   Poll Tax
   Poor Relief
   Post Office Staff
   Precognitions (trial)
   Presbyterian Church
   Presbyteries
   Principal Register (deeds)
   Prison Registers
   Privy Council
   Privy Seal
   Probates Resealed
   Probative Writs Register
   Processes (court cases)
   Procurators (lawyers)
   Professors
   Protests Register (deeds)
   Pupils (kids under 14)
   Quakers
   Railway Records
   Regalities (districts)
   Register House Plans
   Registration of Title
   Relief Synod Ministers
   Remissions (criminals)
   Rentals
   Retours (deeds)
   Roman Catholic Church
   Sailors and Seaman
   Sanctuary for Debtors
   Sasine Registers (Deeds; but remember few Scots owned land)
        These are in large books (self-access) and are indexed by
        shire and year; and then both by place and by person.  The
        index no's are then looked up in the relevant sasine books
        which provide a summary of the transaction.  The no. at the
        bottom of the entry refers to the original document which
        can be requested.
   School Boards
   Schools
   School Masters and Pupils and Inspectors
   Secretary's Register (sasines)
   Sequestrations (tenants)
   Servants
   Service of Heirs
   Sheriff Courts (good source)
   Ship Passenger Lists and Crews and Masters and Owners
   Shop Keepers
   Sick People
   Signatures
   Skinners
   Society in Scotland for Propagating Christianity
   Society of Friends (Quakers)
   Soldiers
   Solicitors
   Stamp Masters
   State Papers
   Stewarty (courts)
   Students
   Subject-superiors (land)
   Surgeons
   Surveyors
   Synods (church)
   Tacks (land)
   Tailors
   Tailzies Register (land)
   Tax Records
   Teachers
   Tenants and Tenancies
   Territorial Soldiers
   Territorials'  Records
   Testiments (wills)
   Theological Colleges
   Tollbooth (debtors)
   Tradesmen
   Transportation
   Transported Criminals
   Trials
   Trinity House of Leith (seamen)
   Tutors (guardians for minors)
   Unemployed
   Ultimus Haeres Records (intestate)
   Unitarian Church
   United Free Church
   United Presbyterian Church
   University Students and Staff
   Vic (grd-son of)
   Valuation rolls
   Vassals
   Voters (and see Electoral Registers)
            McG's on the 1861 Glasgow
Lists
   Weavers
   Whale-fishing seamen
   Wills (need to know approx date & location) post 1800 are indexed
        but are rarely worth the effort.
   Witnesses
   Workmen's Compensation
   Wrights
   Writers (lawyers)