I've seen in several places that picking up familiars with Eldritch heritage or the wizard's arcane bond are incredibly favored with theorycrafters and the community in general.
How do you utilize these critters to their full potential? I've seen most players with familiars practically forget they have them.
Depends on what you want and how much you want to invest. Simply going for a bat like lemeres said for easy access to blind sense is a good deal. The initiative boosting familiars are popular, and having alertness (while not amazing) is handy. One thing is it can depend on your archetypes. The valet familiar gives you access to accelerated crafting and teamwork feats (say something like Escape Route).
Sage can be good for sorcerers, not so much for wizards, turning them into a decent knowledge monkey.
The mauler is good for Eldritch Guardians and could be put to decent use by a Magus.
If your willing to spend the feat, the improved familiar list can get you a decent amount of utility, though mostly it allows for making them into a wand monkey. Keep your UMD maxed and now your familiar has Max UMD.
But generally, given that most familiars have the ranks you do there is basic utility in having them help with perception rolls (if you keep it maxed) or using Aid Another for a small bonuses.
At level 5, a Protector familiar will gives you +2 AC and an effective 50% increase to your HP, in addition to its regular skill/save/initiative increase. Also remember that familiars have senses and intelligence too, so they effectively grant you a second roll on all perception, sense motive, and knowledge checks. This stuff can be done without the familiar ever having to leave your person, so it's easy to micromanage.