@ LisaK - What you can expect: First, I recommend using a blender to make a pale orange emulsion of castor oil & OJ. I use 8 oz OJ to 2-4 oz of castor oil.
I recommend chugging this on an empty stomach, at bedtime. Wear a diaper, you might fill it while sleeping! Normally, you'll wake up in the morning and head straight to the toilet. Don't make plans for the next day that would take you too far from the loo! You may get 2-3 more BM's as the day progresses.
If you want faster action, Drink it during the day, but only if you can stay home. Activity speeds it up, and I usually start feeling it in about three hours. I've had some action as soon as an hour and a half, if really active. BTW, I usually feel some mild nausea for about thirty minutes after drinking it.
I my experience, you do get a feeling that something is going on "down there" about fifteen or twenty minutes before that first explosive expulsion.
The more water you drink, the better. It will guard against dehydration (the risk is small) and increase the thoroughness of your cleanout.
I strongly recommend a series of soapsuds enemas about 4 hours after you after the "urge to purge" has stopped. I usually that 2, 3qt SSE's, and a 3 qt salt and baking soda rinse. I find that the rinse usually comes out looking like it went in, with a slightly straw colored tint.