I'm still pretty new to the trading scene, but I use:
1) general trade guidelines (it's posted somewhere on SC) to gauge what the other person may be thinking
Hand picked coupons are usually traded at $5 per stamp plus a stamp for postage
$20 hand picked coupons - 5 stamps
$50 hand picked coupons - 10 stamps / $5 GC
$100 hand picked coupons - 15-20 stamps / $10 GC
HV/FPCs are usually traded for other HV/FPCs
$10 worth of HV coupon(s) - same / $3 GC / $20 reg coupons
$10 worth of FPC coupon(s) - same / $5 GC / $25 reg coupons
2) what the trade is worth to me

