You didn't give us much info to go on... I would comment that if the clock is not running very long it may not be a hairspring problem.. unless you see some obvious problems with the hairspring. Rather, it may be a problem with the rest of the movement needing cleaning and servicing.
After you read the material Phil directed you to, please come back with more info if you need further help.
I agree with David. I would also add that it can also be a worn or bent balance staff pivot or worn pivot hole. It can even be due to someone applying the wrong lubricant on the wrong spots. What kind of balance wheel clock do you have? They range quite a bit in design and construction. A photo or two would help, especially if you have one of the balance and hairspring.
Thanks to all for their responses. The clock has John Wannamaker, 2 jewel, Germany embossed into one plate. Sorry I can't do pictures right now due to problem with my camera. I let all 3 of the clocks springs down and removed them. Cleaned the movement, while still assembled, but in a good solution, washed it in alcohol to pick up any left over water and dried it thouroughly. Then oiled the movement with top quality clock oil. Checked all of the gears to see if there was excessive end play and all seemed OK.
I did oil the spring cups - was this wrong to do?
Also there are 2 wires side by side that fit into the crutch rather than one. One of the wires is shorter than the other. Is this correct or should they both be the same length? Maybe only one should actually fit into the crutch and the other fit outside of it.