If it's small/built on the ground, something like this might work:
Going larger? Try Lowe's deck designer:
Here are some videos for you to take a look at. There are some great ideas here.
Here's a great post on building a deck step by step. Hope this helps!
The easiest way is to buy the concrete footers with a slot on the top to fit the floor joists in. https://www.youtube.com/watch?v=DsiyEnbR9EQ&t=20s