Drive around in areas where you would like to live, and look for homes that appear to have been recently built. Try a Saturday or Sunday. Approach the homeowners, and ask if they recently built their home, who their builder was, and if they would recommend that builder or build with him/her again.
Check with the BBB in your area to see if a builder has complaints or a track record on file.
In my area, public records are available. You can find many bits of information, including if the builder has filed for bankruptcy, is being sued by anyone, is in foreclosure on any properties, has a valid business and/or construction license. Find out if you have access to that info in your area.
If you find builders that seem to be reputable and are building a product that you like, ask them for references of homes recently built, and then talk to those homeowners.
Since this is your first home, you might also want to consider getting someone else on your "team", wheter it be an attorney, home inspector, and/or a Realtor.
Some builders will not sell you a lot in their subdivision outright, but require you to build with them. If you want to buy your own lot first, then select a builder, you should make sure your lender will permit this (unless you're paying cash outright for the land) . You'll also want to determine if you want to obtain a construction loan, or if you can, and look into the fees and terms relating to them.