I started riding about a year ago and this is what I've learned and in no particular order...
1. Don't let your "goods" go to sleep on your saddle. It may be very important for you to search for the best saddle for your anatomy and riding style.
2. Get some really good shorts or bibs with a nice pad.
3. Get a jersey. I rode most of my first year in a tee shirt. Jerseys keep you fresher and dry and have great storage pockets for food, cell phone, water bottles, tubes, etc.
4. Speaking of water bottles, you MUST hydrate. It's really important to keeping focused on the bike and not feeling like crap after a long, hot ride.
5. Have fun. Change up your routes a lot. Enjoy the bike and if you don't feel like riding, don't.
6. Be careful. You can't ride if your injured or dead. I try to do most of my riding in low traffic areas.
7. You will flat. Carry a tube, some tire levers, a pump and/or CO2 with inflator. Again, you will flat.
8. There is a lot of BS on this forum. But there is also some folks who have some really good information. It will not take you long to distinguish between the two.
9. You will get faster. Just stay after it and ride.
Hope this helps!!!