Orpington's were hit or miss for me when it came to setting eggs. Generally, gamefowl will be the best setters meaning, they will start setting earlier and go full term, the full term is the key as some breeds will start but quit after a while and thats not good. To get them started is pretty easy just leave the eggs in her box and usually after 6+ eggs (this depends on the hen some more, some less) you will notice just before shes ready, she'll start clucking more. Some breeds are better at brooding than others, example, Rhode Island Reds are bred to lay eggs they can and will set in most cases but overall prove to be undependable in the long run. Check in the chicken forum for the best breeds for brooding another point to keep in mind is the size of the chicken, many will say silkies are the best setters but pea eggs are huge. Hope this helps.
Gerald Barker