DeSantis just needs to sit tight and keep his powder dry for at least a year. There will be PACs out there raising money for him up the kazoo. But he should not get in until the clamoring for a viable Trump alternative is at fever pitch. Meanwhile, as Trump campaigns without any significant opposition, he will likely do his usual disgusting schtick against a man who is not even in the race, making DeSantis all the more likable.
The key for DeSantis is not to take any of Trump's bait. Just smile and say "I am focused on the people of Florida right now. They are my primary concern." Rinse and repeat.
I think DJT's act is wearing thin with all but the core MAGA crowd. I would hate to lose them because they are very decent, patriotic people. But make no mistake. IF DJT thinks he is going to lose he will try to blow the whole thing up and pull as many of his people out with him as he can. So it is a very delicate situation, especially if DeSantis decides to return the fire that is undoubtedly coming his way.
So long as the GOP nomination is DeSantis' for the asking, DeSantis need do nothing but wait until the asking becomes begging.