The trays you buy annuals in are great to start seeds. Many nurseries will give you a few if you ask.
Transplant them after they show about three or more sets of regular leaves, not counting seed leaves.
Depends on what type of seeds they are. I personally never "mess" with seeds. I buy plants. If expense is a concern, you can always buy the smaller pots--they are much less expensive then the large ones. They all grow into the same plant. The smaller ones just take a little bit longer sometimes.
