I've found labs difficult thus far. Best thing is to find out what experiment you're going to be doing in advance and then try to get hold of a copy of the lab script for that experiment.
Another thing, my biggest issue, is essentially confidence. Read your script, expect it not to make complete sense, ask for a standard overview of the apparatus from your demonstrators and then PLAY AROUND with the apparatus. I always worked well shoved away in a corner working on my own, for instance when my lab partner didn't show up, since then it was just my own little project to crack on with and had no choice but to, quite literally, EXPERIMENT. Writing this i think it sounds daft, but it's very easy to just resign yourself to not understanding the experiment, especially when there's 2 of you think the same.
As for a difficult lab partner, or one equally as dumbfounded and reluctant to just try things out, I'm not sure what the best ploy actually is.. perhaps asserting yourself and then dragging him into the work by your own getting on with it, or if your partner is a bit of a domineering swine then.. well.. they're the tricky ones, especially if they're good, but I think that little bit extra time in the library before your next day of practical will have you on track