Sugarhill, are these ws babies, or sown in a warm enviornment. If you have winter sown babies, I'd leave them in their pots until we have a few more mild days AND nights not so cold. Just so they can get acclimated in decent weather.
Anything else, the normal rule of thumb is two sets of true leaves. HOWEVER, some plants grow with true leaves, but not many. For example, Borrage can be transplanted with the 1st two leaves as they are sturdy enough. Very nice thick stem.
I like to wait a bit on my seedlings if they are not too crowded. I like them to have 3-4 little roots, then plant them on. If crowed, 2 sets of leaves and one baby root is fine.
To prick out, I've been using bamboo screwers from the $$ store. You get a nice big packet.
Good luck, and have fun! I find the potting of of seedlings one of the most calming and gentle things about gardening.

GGG

GGG, thanks for the advice. I think I'll let them go a little longer just because they are so small right now. I was only thinking about it because I didn't do a very good job of sprinkling the seeds when I sowed these two groups. Several are spread out, then a bunch are grouped together. I still think they need to be a little bigger though.

What are bamboo screwers? I'd like to try it.

I like transplanting seedlings, too. Sort of meditative.

Bamboo "skewers" are for rumaki and shis-ka-bobs. Like long toothpicks they are also usefull for starting vines and supporting young plants and making small holes in the soil. I like chopsticks for this also. For transplanting small seedlings I use a pair of long nosed Forceps I got from my doctor. They throw these away constantly after minor surgeries and will usually give them to you if you ask.

I like to sow my seeds in plug flats. Most of the ones I have are 200- or 288-cell. If you wait until the seedlings have enough roots that the plugs will come out with the roots and soil intact and then pot them up into about a four inch or smaller pot, they have strong enough root systems that overwatering is less of a problem.

Fred

Fred, that's one of the reasons I went back to putting single seeds in paper pots. The plug flats are hard to find something to go over the whole flat for winter sowing (or are for me). I love those for late summer sowing of wallflowers, calendulas, ornamental vegetables, snapdragons etc. Especially with the larger size hole in the bottom so you can really give them a POP, outta there. The paper pots I could put inside the bakery cake domes which I get for free. Automatic humidity chamber for winter sowing. Also great for rooting cuttings.
Vroomp, the forceps are an excellent idea! I see the surgeon tomorrow. I'm going to ask for some!!

GGG