I've heard of sticking a shed from another male, preferably one that is breeding, in the same enclosure as the new male and his hopefull mate. Also taking the sperm plug from another male and rubbing it on the female. Take the substrate from a pair that is locking and put it in an enclosure with a pair that isn't. Also using a proven breeder female can sometimes help.
We got a proven male and he started right away with his female. We have a male pastel that we tried a couple of times late last year and he didn't do anything then, but this year we put him with a female and in a day or two he was going to town. We put a totally unproven male in with a proven breeder female we had gotten from another breeder and it took him almost 3 months of 3 days on, 3 days off, before he finally locked. A couple of times prior to the lock we saw him pushing his tail against her trying to get there, but never succeeding within the 3 days on cycle. We just started another pairing but the female, while over 1500 grams, is the youngest we have tried, June of 2007 born, to date so we are not very hopeful with that pairing based more on the female than the male. Beginning of January we have an 2006 girl who should make the 1500 gram mark and we hope to give her a try, but we are still unsure of which male to try her with.