Sources
Most frequently used:
Maps
from National Library of Scotland
maps.nls.uk especially the geo referenced ones allowing you to overlay a modern map
Farm Tax Rolls 1797-8 on scotlandsplaces.gov.uk
Old Parish Records (abbreviated to OPR) - baptisms marriages and burial before 1855 on scotlandspeople.gov.uk
Censuses 1841 - 1911 mostly using transcriptions from freecen.org, ancestrytry.co.uk or findmypast.co.uk The 1911 census and all the original images 1841-1911 are only available
Valuation Rolls 1855 - 1940 on scotlandspeople.gov.uk (abbreviated to VR)
show the proprietor (land owner) and the tenant/ occupier
British Newspaper Archive (subscription) and old Cumnock Chronicles, not online
Our own big family tree Cumnock Connections
Also
Canmore for photographs which is part of Historic Environment Scotland
Future Museum for photographs
Old Statistical Accounts