How to mend a tap ?

I do not know what type of tap U R referring to but:
1) U should have H&C valves under the sink - close them.
2) The supply lines from the valves to the taps have to separated. Same procedure whether it's taps (as U R calling them) or, a single lever faucet.
The supply lines can be a braided stainless steel looking type of material, 3/8th. copper tubing or 1/2 in. brass or galvanized nipples (depending on age etc.
3) U will possibly need small pipe pipe wrenches, channel locks and or an adjustable wrench.
4) Discard old or worn parts & replace in reverse order.
5) On completion, turn valves back on slowly - check for leaks & let water run for a few seconds - you'll probably have rusty looking water or sediment until it clears up!
Note: Worst case scenario: If there are no valves at the fixture or, the valves will not hold, you'll have to shut the main - in which case, the valves will have to be repaired or replaced.
Additional items: Teflon tape, putty, WD40, rags, newspaper.
Wishing U luck !

Cary.
December 2008