Ian H
Ancient randonneur
Tips and tricks: use the thinnest rim tape, and as narrow as will still cover the spoke holes. Use plenty of talc or chalk as a lubricant. Although it's a good idea to put a little air in a tube when fitting, you might need to let it all out for the last part of fitting. As Screenman said, above, make sure the bead you're fitting sits in the centre of the well of the rim everywhere except (obviously) where you are pushing it over the rim - push the tyre into the well as you progress round the wheel (you might be surprised at how much difference that simple action makes).