Ride your bike at a faster than normal pace (unless you're a stravaite), have fun, let faster riders pass when/if you can. 

IMO when it comes to racing on trails like BYT where it is tight and technical, you may have the pace to keep up with the front pack, but if you get caught behind some wiseass Enduro^TM jockey it could get you separated from the main pack and youll have to push to pick them off or even catch up. Thats just the nature of mass starts. This is all provided you're going the right direction and everyone else is as well. lol Can't hate on that, its the nature of the beast and each event has its quirks and some people are faster on certain trails that fit their riding style. 

If you're going slow and holding up a pack, it is the responsibility of the overtaking rider to call his/her pass, but don't be a putz and just hold up the pack. In the rare occasion I am passing someone, I use the desert racing etiquette method which is Beep Beep Bump. Call the pass, call it again to make sure they acknowledge and if they refuse to acknowledge you are there, and if they are just an inconsiderate jackass and refuse to let you pass just pour the heat on til they get it. I'd never actually bump the rider, but do what you have to do within reason to make your goal known. 

In the end, just go out there, have fun and race your race. Some people may race for 1st, others may race for just not getting lapped. Races like BYE are all in good fun. I was in Boone/Banner Elk on Saturday and am sure there weren't people at the Collegiate Nationals or Wilkes 100k flinging syrup covered waffles at racers or crushing a beer between stages. Same goes for Short Track season. Vuvuzelas, air horns and a group of us standing around booing people who don't hit a 8" tall jump are all part of it. If there is a way to get into racing and have fun...start with Short Track this winter. Its a lot of fun and we all go out to have a good time and heckle each other.

I second the Short Track as a great place to "get your feet wet". Passing is not an issue there. It's cold, but don't over dress. 

Another good place to start is in the 6 hr races. The pace is more relaxed and you have all day to get the hang of it. 

In the regular races, I'm slow and haven't had a problem with being passed. Most racers will let you know they want to pass. If they come up on you really fast, get out of the way. If they slowly catch up to you, ask them to wait for a wide place in the trail. 

I'm over 60....so If I can do it , you can do it!!! Just go and have fun.

You'll have a blast at winter short track. Start off at the back of the pack so the pressure is low and pick off as many as you can for a confidence boost. That was my game plan. I was normally dead last heading into the woods. This way I'm the only one doing the passing. Except when I was getting lapped of course