1. Highlight film. Even with just a few clips you can see how much explosiveness a kid has (first thing i look for). Sometimes a kid will pop off the tape and you really don't need to see any thing more. Also can give you a good indication of their competition and size.
2. What schools they hold offers from is key to. If they don't hold offers from a feeder or home town school, this is usually a red flag. Either they're garbage, or there's some other issues going on (grades, psycho, etc.) that they know about that others don't or will soon discover.
Not that I disagree with you but...here's the grey area with both of those...
1. He may pop off the screen athletically, but it's a HIGHLIGHT tape. There's kids out there who show great ability for a few snaps a game but are irrelevant and make zero impact for the rest. However, I'm aware of the fact that college coaches just wanna see ability and they believe that they can coach up any kid who has it.
2. I don't think you can apply this rule to South FLA kids. Just because a South FLA kid doesn't hold offers from UF, FSU, UM, etc...doesn't mean he's not a stud. There's 203,320,012 Division-1 recruits in FLA. Not all of them will receive offers from the likes of UF/FSU, especially South FLA kids, as UF/FSU usually only come down here for the elite kids. There's South FLA kids who didn't receive offers from UF/FSU who could easily play at Miami and help us greatly. A kid may not have offers from UF/FSU but he'll have offers from Clemson, Oklahoma, Nebraska, Ohio State, Michigan, etc. (other top-25 teams) That kid can likely help Miami.
Now, if a kid doesn't have any offers from top-25 schools then I'd consider it a red flag. Golden was a huge fan of signing kids who's offer list had Akron, Western Michigan, etc.