1. If you don't like doing shots, then you shouldn't do them. I like strong spirits like rum, whisky and sambuca but I don't like vodka - so I just don't drink it, and when my friends buy it I refuse to drink. Although this makes me unpopular for a few minutes, eventually they learn.
2. Doing shots: what I do is a take a quick sip of it when it comes. This gives my mouth a taste of the drink and it's not so much of a shock to the system!. And I think that stops the 'reflex'. Although this is pub science, and I may be completely wrong!!!.
Also a good thing is to get used to the drink. So at home or wherever, you should start drinking it just like a normal drink. Again, I didn't like rum when I first had it, nor beer- but I have learnt to like it.
3. If you are just not a strong spirits person then you should consider doing Apple Sourz or something else weak when others have their rum/vodka.
One final baaaaad tip that you shouldn't do. Is when you are preparing to take the shot. Take the glass and sort of tilt it out of the way of your m8s.... this will get rid of some of the shot. Over time, you can become an expert at this and eventually you only drink half a shot!. This obviously is a waste of money, but it avoids your m8s taking the mick from you.
True story- we once had a very strong spirit when I started going out. And I though I just cant drink it. I managed to tilt the glass enough that I only drank a drop of the drink.... and nobody ever knew!! (but obviously I did the usual reaction of "urghhh this is disgusting" "wow strong stuff" etc