Hi TimTim,
Firstly good luck for next Tuesday!
Secondly, if you have a good fit you should find (fingers crossed) that your lenses will stay in quite snuggly. Its not always easy for your speciailist to get a great first 1st time around but usually, the better the fit, the more likely the lenses are to stick around.
However, in answer to your question (on a personal level, this no doubt will be different for others) I find the only time my lenses try and make a run for it (pun intended) is when they dry out - blink often enough, keep them lubricated and they tend to stay in like those plastic sucker things.
I tend to find my lenses most like to jump out when I'm cycling, but I've cured this in part by always wearing wrap-around shades at the same time - this reduces the drying effect of the wind and also acts as a kind of safety net if they do dry out.
When I go swimming I prefer to take them out - mainly for hygiene - I think what little boys do in swimming pools (sorry for the image) and I worry about any infection I may pick up from the water and into my eyes. I go swimming (when I do) with the other half and so there is always some there to guide me should I confuse the lifeguard with the way out

Lastly to the shower - if you can see to wash without them take them out. Otherwise soap in your eyes tends to be worse that it already is. Plus it gives your eyes a rest and allows you to rinse the rubbish out of the corners of your eyes without fear of catching the lenses.
Hope this helps.
Ed