This year I started three kinds of basil. Genovese, lemon, and a lettuce leaf variety, all from Baker Creek Heirloom Seeds. This is my first year planting them with any notable success, and here's what I learned.
A few weeks before the last frost I planted the basil seeds indoors, under a grow light, with no added heat. The seeds sprouted quickly. You can see the genovese basil to the left with the rounded, shiny true leaves, and the lemon basil to the left with the non shiny leaves.
After a few weeks I had to start thinning them out, so every week I pulled the least robust seedlings. At the beginning of may I planted a few of the "culls" outside near my tomatoes while it was still pretty cold, fully expecting them to die. Towards the end of may I finally decided to put my basils outside after babying them for such a long time and I learned something interesting.
The basil plant that had been outside the whole time had developed a fibrous stem and robust leaves that didn't burn in direct, full sun. while the basils that I babied for an extra month were practically melting. My lemon basils struggled the most out of all of them.
My conclusion being that babying plants won't necessarily give you the best results. Even though I kept the most robust seedlings indoors and planted the weakest ones outside, they're now outpreforming the ones I coddled.
On another note, Baker Creek's lettuce leaf variety seemed to have a super low germination rate. I sprinkled at least 10 seeds into the pot and only three sprouted. One took off, the second one grew very slowly, and the third stayed very tiny for weeks before I pulled it. That said the one that did grow is absolutely gigantic. It's significantly larger than any of the other basils I sprouted at the same time.