Depending on the herb, about now is the right time to cut them, I usually wait until things like Oregano and thyme are in flower, then cut them back, and use the cutting to dry, this helps stop the plant putting too much energy into the flower and seed, and at this time of the year gives a chance to put on new growth before the winter. I don't dry rosemary, as I find it goes too stick like, and it has green growth all through the winter any way. Sage is good to cut now.
Be careful not to over cut into old wood, as this can kill them.
All I do is make a bunch , tie it with string and hang it up for a few weeks in a dry airy place (our pantry next to the air brick which is near the roof

). It does not have to be particualry warm or anything.
When they are dry ( usually a few weeks) I get a paper bag and put the bunch into it, scrunch the herb into bits, picking out as much stalk as possible then I put in small kilner jars for the winter.