All players on negotiatons list need 1 skill point to become scout. Younger players are (of course) better. You can also take a look on team in which player is to check out if this is substitute or 1st team player, how important is he for this manager, how active manager is etc.
To do that, click on right manager picture (marked with red arrow on this screenshot)
Click image for larger version.  Name: negotiate.JPG  Views: 17  Size: 63.6 KB  ID: 30831

Then decide to send offer. If you have much tokens, send him offer money+few tokens, he will accept for sure if he is active.