Go to the bookstore
There are some expensive and semi useless estimating books.
Craftsman NATIONAL REPAIR & REMODELING is one, Gives you aprox. time materials overhead. It's a starting point only.
BOBS advice is good you really need to figure each job and the unique factors of that job. Be careful of falling into the PRICE PER SQUARE FOOT nightmare. Think about this one example: tile setting 6.50 sf.
400 sf basement 1 day to set -one half day to grout

35 sf bath floor 1 day shot - 1/2 day shot:no:
22 sf back splash 1 day ruined - 1/2 more trashed
PRICE PER sq ft not to good. How would feel on payday if the customer remeasured your job and found your number was a few square foot high?
Best luck and welcome to the group
MIKE