I would suggest going for walks up there first and sussing out the good ground, lines and which directions to best tackle stuff, especially if you don't know the area. The best place to start from would be the main car park at the cow and calf rocks/quarry. That whole hillside is Bradford council access land and there are some superb techy lines and many more lines which don't work on a bike. The best ground is generally on that hillside, if you go onto the moor top then you have to be more careful to pick and choose your routes, because many of them are delicate and boggy. As a rule of thumb on the moor top, the ridge lines tend to be the more solid and therefore best riding. Don't ride on the moor after rain, let it dry out for a few days/week, don't ride it thru the winter. You're not really supposed to be there, but the owner, Bradford Council, tolerate biking on their land, so be very considerate to walkers etc, slow down for them. Best to ride it when there are not going to be too many people wandering around, i.e. not on a warm sunny sunday afternoon, maybe better on a monday evening.
So roughly, a good route would be, start from the cow and calf car park, ride down on a path (parrallel(ish) to the road) to the pond, work your way across to Keighley road (traverse/trend generally upwards rather than down), then climb up keighley road to the twin masts, turn left and ride across the ridge line to the stone circle (get on the ridgeline rather than the flat boggy ground), down the path to ridgeline overlooking Ilkley, down the fantastic descent, turn left and ride thru rocky valley, down and pass to the right side of the tearooms(white building), traverse down back to car park on a good track.