Telling a good layer?

[Rowzy]

So I was at the feed store the other day and they had a fair bit of hens. They know they are laying a lot but they don't know which hens are laying.
Is there a way to tell if a hen will be a good layer? (like if shes old etc she won't be a good layer right?)
I also saw 4 silkies they had but they think they are all roos. How do you sex a silkie? 3 had rose (?) combs and one had a single comb if that makes a difference. I want a silkie because I heard they are great setters and none of my hens are setters. (Plus they are ADORABLE)

 

[wings]

If they have a wide body, that's a good sign.

I have a chicken bible by Gail Damerow, Storrey's Guide to Raising Chickens. It's very helpful!

 

[Lollipop]

Well....... I can tell ya how to tell if a hen is laying, but a lot of factors enter into the equasion on who is a "good" layer. OK, to determine a hen is laying, above the vent are a couple pelvic bones. A large hen that is laying will have enough room between those bones to place at least 3 fingertips. Smaller hens somewhat less room. Now, don`t get excited, I`m not advocating incerting your fingers into her vent. The pelvic bones are above the vent.