My band has an upcoming gig where we will either going into the PA or they will be miking the amps. Is there any equipment or devices needed if I DI or do they just plug in to my amp? My amp has a DI port. If I have a choice of DI or miking the amps, which is better? I heard the sound can be a bit sterile when going DI or is that just a function of the soundguy?

I use the Direct Out on my amp for the PA. This way I get the purest sound and the soundman has more to work with. If you mic it, you'll be getting the limitations of your cabinet and the limitations of the mic subtracting from your tone. For example, the cab can't reproduce the highs cleanly or the mic's electronics are weak on picking up lows. Unless your cabinet makes your tone awesome and is what you hear when you think of your sound, stick with the DI.

I use the Direct Out on my amp for the PA. This way I get the purest sound and the soundman has more to work with. If you mic it, you'll be getting the limitations of your cabinet and the limitations of the mic subtracting from your tone. For example, the cab can't reproduce the highs cleanly or the mic's electronics are weak on picking up lows. Unless your cabinet makes your tone awesome and is what you hear when you think of your sound, stick with the DI.
I was all set to vehemently disagree with you until you said that last sentence. I started micing again recently and now I don't even use a DI, but then again, I do have awesome cabs ;)

I would say mic if you have a cab you like the tone of, but go through the amp's DI or use the soundman's DI if you don't.

You can use your amp's DI, but many soundmen prefer to get your signal with an external DI after your bass and effects and before it hits your amp. DI's in amps can be noisy and low quality depending on the amp. Of course catching the signal before the amp will also remove any amp coloration from your tone. This is an issue for some bassists, but not for others (like me). Though many do, I would never choose to mike the amp.

I have Markbass LMII and I'm not sure if it's the line out on it or our bands PA but I really don't like the bass tone coming out of the monitors/mains. I've only got a single Avatar B210 but the tone coming out of it is much better than what comes out of the PA. Actually, the monitor signals are only mixed from the PAs board, they have their own power amps so that further confuses things for me. Oh well, I just turn up my amp so it sounds good to me. :p

I vote for running a cab if you have the space on stage and you can keep it down enough not to interfere too much with what the soundperson is trying to accomplish.

I'd go with the soundman.
If they want a DI, they'll have a spare for you. They could use the one on your amp, if there is one, but they'll be worried it's post-EQ - you can really fvck things up this way if you tweak your eq significantly!
Typically they'll take a DI off you post guitar and effects and pre amplifier and you'll sound just fine.
If you're really picky about your amp/cab tone then get them to mic you up.

Ric