Since I have never had much success with outdoor-grown Basil (lack of warm sunshine is to blame), I have taken to growing some in pots indoors on a windowsill, where it does quite well - especially since the windowsill has a central heating radiator right below it.
My plants normally last about a year before they lose their vigour and need replacing. Last month (Feb 13th) I sowed some Basil seeds ready for this years plants. I put about 20 seeds in a 6-inch pot, and when they germinated I thinned them out a bit, to give them enough room to develop properly.
Today I judged them ready for transplanting. Each seedling had at least one pair of proper leaves (i.e. discounting the cotyledons); some had a second pair just forming.
About an hour before transplanting I gave the seedlings a good drink. This makes it easier to move them with a fair bit of compost adhering to their roots, thus minimising transplant shock. Then (since I had 9 seedlings) I filled four 6-inch pots with fresh compost and moved the seedlings into them, two per pot:
Guess which one didn't make the grade? Yep the little "runt" seen at the left in the photo below...
These pots have now taken their place on the Dining-Room windowsill.
Meanwhile, this was the fate of the plants from last year - frozen cubes of pesto!