First and foremost, do yourself a favor and get a lesson. This is the best way to ensure a fun and safe first surfing experience.
That said, ideal conditions for beginning surfers are small, gently breaking waves and minimal crowd.
Ideal board is approximately 9'-10' and preferably a soft-top (soft boards hurt a lot less when they hit you).
Once you're on the sand, spend some time watching the surf and the surfers. Where are the waves crashing (look for whitewater)? Where are the channels (areas where the water is deeper and the waves don't break - look for blue/green water)? You can't fight the ocean, so it's best to go around the whitewater (in the channel), or rest for a minute if there are a lot of waves/whitewater pushing in.
Depending on how big/consistent the surf is, you might not even make it out past the whitewater, which is fine. Whitewater waves are great for getting your first rides. Just point the board directly to the beach, start paddling right before the whitewater gets to you, and brace yourself as the whitewater hits you. Then stand up, keeping your knees bent and arms out.
Most importantly, always check with the lifeguard about the conditions, and "when in doubt, don't go out."