Go there ahead of time if you can. I know from experience that if you just jump in there at peak hour you're going to get overwhelmed with noise and (for me anyway) that can throw off my orientation.

Definitely echo what others have said. In every new pub or club I go to, I make sure I have a basic idea of the location of the bar, bathroom, entrance/exit, and any other outdoor areas for smoking if I want to get some air. Sure, I might get lost or look lost the first few times I venture away, but it's a perfectly safe space for me to get things wrong and learn fast.

Remember that almost every pub and club you go to will be some variation on a square or a rectangle with bits cut out on different sides. When I internalised this, learning the lay of the land became simple educated guesswork. Bathroom door not along this wall? Okay. That makes sense. This one feels too long to house a bathroom. The windows and tables certainly don't help. Ah well, let's keep going and hopefully it'll be on the wall in front of me.

As the night progresses and you get talking to people, don't hesitate to ask for clarifiers on things if you're a little unsure. "is the door to the bathroom I need the only door in that area, or is there another one next to it that I should be aware of? When the drinks start flowing, an arm to somewhere a bit too tricky to access is perfectly fine.

Have fun, and make the night work for you.

Yes, agree with the others. If you can definitely go ahead of time, find everything you might need, ask if not, and generally get o know the area you'll be in (and how to get to/from it).

For me, the big thing is just knowing where the bathroom is. Definitely go early and try to scope out the bathroom. If you can't find it, explain your situation and ask the bartender.

Get there early and walk around the bar for a bit. Find where the bar, restroom, DJ, Karaoke stage, and the exit are located. I've always found that people in bars are cool and helpful, but you'll probably feel more comfortable if you know where stuff is located.
You could ask the hostess or wait staff for some orientation to the bar.
The cool part is that you can come often and become a regular, which will make your evenings better as time goes by.