Certainly far from an exhaustive list (watch those youtube videos) but here are some tips:
Removing:
1. make sure as much of the air is out of your inner tube as possible
2. when you've done that, push your valve up a bit into the tyre
3. be careful not to pinch the inner tube between the tyre lever and tyre (that's a puncture waiting to happen) when you are levering off the tyre
4. lever off just one side at a time -the opposite side will then be easy to remove once you've removed the inner tube! (and remove that inner tube too, it will make it easier)
5. Once you've got a bead off, usually you can slide your other lever around in between the tyre and rim rather than having to lever off the tyre at different parts of the rim.
Installing:
1. make sure one side of the tyre is seated, put your inner tube in.
2. usually you can just use your hands (except when a tyre is really difficult) to push the other side of the tyre on.
3. make sure your valve is pushed in a little bit when you seat the tyre -you also help prevent pinches by partially inflating that tyre which will help to seat the inner tube inside the tyre. Be careful though; you don't want to inflate too much.
4. BEFORE you inflate your tyre fully, ALWAYS go around the tyre on each side to make sure the inner tube isn't pinched. Just press in the side of the tyre and you should be able to see your rim tape, and not the inner tube. Start at your valve to make sure you go around fully.
5. once you've done this, you should be clear to pump up your tyre to the appropriate pressure, and secure the valve if it has a lockring.
6. one last thing: orientate your tyre so that the label is at the valve -it's a small thing, and admittedly not necessary -but it really makes finding that valve so much easier when you are in a rush!
I should also add it's a good practice to feel inside your tyres with a finger to see if you have any stuff that might cause a puncture too. Oh, and sometimes you might get a nasty combination of a slightly larger rim with a slightly smaller sized tyre that can require a good amount of brute force -so if you feel it's really really difficult, this might be the case.