I've been researching my father's family for the past 15 years, and have uncovered 4 ancestors that fought in the Rev. War. It's been a fascinating journey.
First of all, get yourself a good software program, otherwise you will be lost and confused in no time. I use Family Tree Maker, and I just upgraded to the most recent version. You can buy it at Costco for $40.
Secondly, start with what you know. Enter into the software program everything you know starting with yourself - your birthdate, the names and birthdates of your spouse and children, your parents names and birthdates, and your grandparents names and birthdates (death dates if applicable). You want to go as far back as you know, or can find out with a phone call to close relatives.
The next step is to search the census records. The latest one made public is 1930. Look up everyone in your line that was living in 1930, then work backwards with the information you uncover. The census records are available online through ancestry.com and elsewhere, but there is a subscription fee involved. Sometimes you can find a kind soul who has access that will look them up for you.
All the sites mentioned above are good sources of information. Let me know if I can be of any help. I enjoy helping others!