What @sneezles61 said. The nice thing about kegging is most mistakes can be easily fixed. Too much carbonation, disconnect the gas and release some until it comes around. Not enough, leave it hooked up and/or turn it up a notch. It will take a while but once you get to know your system you will wonder why it took so long to keg.
One suggestion. If you are only force carbing in freezer, CO2 dissolves faster in colder temps so try in the 30s. If you are serving one keg and force carbing another you may want the temp higher for the serving keg. It will still work to force carb but may take longer.
Definitely check for leaks. It sucks to blow out a newly filled tank the first day. Also consider a spare tank. They know when it is Sunday, you have a gang at the house and the CO2 guy is closed. Ask him about just paying a deposit rather than owning the tank. When it is time for the tank to be hydrostatic tested, it will be the CO2 guys problem. Plus many times you can just swap the empty for a full without waiting. The tank might not be nice and shiny but it's what's inside that counts.