Check out the Winter Sowing Forum! You will be amazed at what is possible. This year my garden is 99% Winter Sowing Babies and they are doing incredible. There are folks on this forum doing winter sowing in zone 1 and 2 and their success has inspired me beyond words.

Here is a link that might be useful: Winter Sowing Forum

Well, actually winter sowing won't give the head start needed for the types of seeds I assume you are interested in - tender vegetables, and annuals that need to be started early. That's because winter-sown seeds will sprout at the time that the weather conditions allow them to - which is the same time that they would sprout if planted directly out, so there is no advantage. Some people use covers on their winter-sowing containers, which forces early germination, but then the seedlings are exposed are cold snaps, and losses are suffered due to freezing. Winter sowing is, however, an excellent and useful method for perennials that need a simple cold-warm stratification.
However, the answer to your question is not really complicated. You just need to get a good fluorescent light setup, then start your seeds no earlier than mid-March and probably no later than mid-April, in order to have good sized plants to set out after your last frost. Room temperature is fine - no additional heating is needed, and there is generally no trick to starting such seeds. Just follow the seed packet instructions, which generally say to start 8-12 weeks before last frost.

I'm a little puzzled though - if you bought pre-started annual vegetables from a nursery, that should have already given you the head start needed for them. Were the seedlings unusually tiny when you got them? Are they planted in full sun? Have you had a really cold season wherever you are? Just wondering, as the advantage to buying seedlings is to save yourself the effort of starting them early indoors...

I guess they start the seedlings mostly for their own area which in a zone 5 so you can't buy seedlings early enough for my z3. If my cukes and tomatos were at this stage 3 weeks ago I would be looking at a nice crop.
This was also a bad year with a cool cloudy spring when we normally have far more sun.
If I ever get my green house built I should be OK.
I really would like to get some early crops as well.
We always have that one late spring frost and then an early late summer frost to keep our growing season short.
If you took away these two days of frost our season would be at least 3 weeks longer.

It's quite the opposite here. The "big box" stores start getting their tomatoes, etc. in in February. My DH used to work at a garden center, and was frequently asked if they could be planted out already!!!

Tomatoes I can get. It's stuff like cukes, spinach, and peppers I can't get early.

There's no point to starting spinach early or to buying plants - just seed it directly in the ground; it's a short season plant, like lettuce.
Cucumbers and peppers definitely have to be started early indoors, if you can't buy big enough plants by the time of your last frost. We can only get mature peppers by growing them in the greenhouse here - cold nights, short season - same for tomatoes (usually), eggplants, squash, etc..

I'm not sure why but if I buy spinach bedding plants I get a good crop, but my seeds go straight to seed.
I planted both this year and the same thing.

Spinach bolts rather quickly here too, so some people sow an early crop and a later one, since it grows so fast. My theory as to why it bolts is that the cold nights here make it rush to bloom and set seed - don't know, just a thought.

please help find my friends sons killer......
thank you!

Here is a link that might be useful: fbi most wanted....jason derek brown

I once heard that it's the amount of daylight we get that causes spinach to bolt. If you plant it later in May (sometimes the only time you can get into the garden), the long days that follow causes it to bolt. No documentation on that, but it's just what i've heard. Back in the '80s (said the oldtimer!), we had several years where we could plant in late April or early May, and we did manage good crops of spinach. Next year i'm going to seed a row as early as i can in a south-facing flower bed and see if we can get a good feed of it again.

I would second Lori's advice on the light setup and starting tomatoes, peppers and cukes on your own. There are things you can do in your garden to help them along, too. We've used black plastic for years for the bed that has those heat-loving veggies in it. It warms the soil (as well as prevents weeds, which is a plus), and you can get your plants in a little early. Cloches and wall-'o'-waters would help all those plants as well. What i do instead is put tomato cages over the plants and put a clear garbage bag over the cage. It can be rolled up during the day and let down during the cooler evenings.

Of course, that gives them a bit of a start, but this time of year is a different story. If an early frost threatens, you can cover your tender vegetables - we use tarps - or get up early and water them as the sun is coming up. It's kind of a pain, but it usually happens that if you have a few cool nights, milder weather follows, and then your fruits have few more days or weeks to live in the sun and ripen on their own.

I see you mentioned that your tomatoes are blooming now (just scrolled back). That might be a problem for sure! Next year, plant tomatoes that have a shorter time from setting out to harvest - Early Girl, Siberian, etc. That's where starting your own seeds is an advantage. You get to choose varieties that suit your own area.

Good luck!