Spectators are always welcome!
A few things to keep in mind:
1) Hearing protection is mandatory. Someone always has a spare set of ears, but best to bring your own.
2) Eye protection: same as above.
3) Find out about the range amenities before you go. Water and lunch may not be readily available. You may have to bring your own.
4) Dress for success: make sure you have appropriate gear for the conditions. Winter = warm clothes, summer = sunscreen and (possibly) mosquito spray.
5) Introduce yourself! Let everyone know you're a newbie and that you are interested in participating one day. You will get a warm reception.
6) It's a competition. Some people may not seem that approachable/stand offish. Don't let that influence your opinion of the sport. Some competitors are very focused and intense when they are preparing to shoot or have just shot a stage. Normally these are very nice and approachable people, but just before they shoot or just afterwards they can be a bit... brisk...
Have a good time!