Know the length of time you have to grow. I have 5 monthes April-August. To grow warmer crops like melons, tomatoes, and peppers. That is about 150 days to grow plants naturally.
Yes my last frost is about March 15th, but I don't but warm plants outside until its hasn't frosted in 2 weeks. It's a safety rule I follow.
I most seed package have how long until the plant matures on the label. So you know when the plant will start to give you fruit or veggies. Now if my watermelon will mature in 120 that means it will start to fruit then so I want a little longer time. Therefore I plant them indoors to give that extra time.