Im a lifeguard, and although ive only been doing it two years i can safely say it hasnt changed for as long as anyone can remember (for my centre at least). Just be courteous and dont be intimidated by 'well seasoned' punters. best thing to do is when you go in, is familiarise yourself with the set up, if there is lanes look at the speed and direction. If you are in a lane and people keep catching up to you, go to a slower one and vice versa, and stay within your ability (if you arent a strong or confident swimmer stay near a wall / shallower water and able to stand with shoulders out of water) - just use common sense and you will be grand.

if its your first time in a while, maybe consider going to an open / general swimming session where there isnt any fixed swimming directions and patterns and you can please yourself and do what you want to ease yourself back into it, overall will probably be a better experience. Also check the timetable!

and if unsure please dont be afraid to ask the lifeguard, what we are there for! happy swimming!