How do you put on bike grips?

Hairspray is the key. Cheapo Poundland hairspray.

If you haven't removed your old ones, use a screwdriver to create a gap between the bar and the grip, and spray in some hairspray. Work the grip back and forth using more spray if necessary until the grips are sufficiently lubricated to slide off.

With your new grips simply spray the inside with some of the hair lacquer shake out the excess, and then slide the old boy onto the bar. The hairspray will set after a few minutes leaving the grips securely on the bars.

Job done.