It depends on the what class you're going to go with. If you're Sentinel, you get 4 skill points with 12 INT. Start increasing Awareness for a few levels until it reaches 18-20. You should have enough skill points to also increase Treat Injury and Persuade and Demolitions while increasing Awareness.
If you go with Weaponsmaster/Marauder as your prestiege class, you gain 2 skill points with 12 INT. By that time, you should have more than enough Awareness. Increase Treat Injury and Persuade. Stop increasing Persuade when it reaches 22-25. After that, continue increasing Treat Injury and any other skill that is a cross-class skill (highlighted in yellow.)
If you choose to go with Sentinel-Watchman, the number of skill points you get won't change. You can increase Treat Injury, Persuade, Demolitions, Awareness.
Note: If you wish to not lose out skill points, go with Sentinel-any prestiege class. Don't go Guardian unless you are willing to sacrifice skill points.
Treat Injury, in my opinion, is probably the most usefull skill to have. Next is Persuade followed by Awareness. Treat Injury determines how much you heal, which is important to both DS and LS.