The answers to those questions may differ depending on your situation. I'm glad my containers are in shade right now, because I don't want them to sprout earlier than they should due to our unusually warm weather. Once April comes around, I'll want them in sun, so they'll warm up faster and sprout and get growing. If I haven't gotten them planted out, or they haven't sprouted by the time day temps are in the 60's, then I'll want them in shade again so they don't dry out or get fried fro the heat. The seed type can also change desirable conditions. Tomatoes and peppers can tolerate much hotter temps, but can't tolerate frost, so I'd put them in a sunny spot. Does any of this help?

Martha

Hi,
I agree with Martha,and --
once you have sprouts you want them to get sun, but not to fry. So depending on your set-up, you can enlarge the holes in the top.
The way I do it, I just roll my cover back, leaving half the container uncovered. You want the spouts to get sun, and to get used to the wind, the air, etc. Depending on the plant you might want to cover again if the temps dip at night.
It is a trial and error thing.
some people take the tops off when the temps rise, and that's it. They stay off. I'm a little more conservative, and tend to do it gradually, until April, when I take them all off.
Be aware that the temps inside the miniature greenhouses are 20 degrees higher than outside. [I actually stuck a thermometer inside to discover that!]
More babies are lost to frying than to cold.

oh yes...and welcome to the wacky world of winter sowing. :)
just keep asking any questions you have. This is the friendliest place on the entire worldwide internet imo.

Thanks Martha and Ellen! I moved some of my milk jugs to the south side of the house and left the others in the shade. Ellen, I really liked that you pointed out that the temp in the milk jug is about 20 degrees higher because that helps me sleep better at night!