Sorry if some of this seems a little obvious but I'm not sure how experienced you are!
Take plenty of spare batteries and wipe your memory cards, whenever you're taking a picture quickly check what's in the background before you press the shutter!
3 standard types of party shot......
1st, full length people shots. Careful not to chop peoples feet off! 18mm will come in handy for this!
2nd, pop round the tables when people are seated (but not while they are eating!) to see if people would like their picture taken and hopefully grab a few posed shots.
3rd, people dancing (if there is a disco) can provide some decent shots just use a faster shutter speed, 1/10 is too slow!!
I did a 21st last week and the main lesson I learned is that I didn't up my flash enough, and had to rescue some shots in PP. Back it off a little for closer shots and up it a little for things further away. Sounds obvious now but it was something I never thought of till I was half way home!:shake:
Other tips are try and take a couple of each shot incase of people blinking, don't be scared to kneel down etc so people aren't always looking up towards you and
always shoot raw so you can sort out mistakes with exposure etc should you mess something up.
Oh, and have fun!!
really aprechiate them !!!