Replaceable-blade heads have become the most popular style because they make creating fresh razor edges nearly instantaneous. If your broadheads have been in your quiver an entire season of stand hunting or a couple weeks of hard mountain hunting, take the extra precaution of replacing them with fresh steel. I know, replacement blades cost money, but in relation to all the other things we spend money on in order to bowhunt, the cost is minimal. Save old blades for practice or small game hunts, marking them with a permanent marker to assure you don't mistakenly use them for big game hunting.

Harsh environments—moist or saltwater atmospheres—can dull blades even while simply sitting. Even modern stainless steel is subject to the effects of oxidation, which moisture (rain) or chemicals (salt) accelerates. Use a trick of archery hunters of old, back when carbon steel and hand sharpened edges were the rule, lightly applying standard-issue, scent-free petroleum jelly to cutting edges. This keeps edges fresh, and even aids slightly in penetration on thick skinned game. I find this especially helpful with mechanical designs, where moisture and grit can accumulate in retention slots to corrode edges.

An issue worth pointing out is broadhead packaging. I won't point fingers, but too many heads come in eye-grabbing bubble packs that make it easy to see what you're purchasing, but also allowing edges to rattle around and become dulled. Never assume heads are hunt-ready out of the box. Test all heads before hunting, touching them up if required, or simply selecting brands that take precautions to protect sharp edges from abrasion. Cut-on-contact, resharpenable heads are often not shaving sharp out of packaging, and should always be touched up before the hunt.

Practical Touchup
Some heads are simply easier to sharpen than others. Two-blade traditional heads are made for re-sharpening and are generally the easiest. With unfinished edges, or those damaged after a shot, start with a bastard file, taking steel off slowly to create the correct edge angle. This is a subject of debate, too much angle creating a fragile edge, not enough a chopping "ax" edge. At one end of the spectrum are heads like Rocket's Ultimate Steel with Bacon Skinner blades, New Archery Products' Thunderheads, or Magnus Stingers, with low cutting angles in the neighborhood of 20 degrees, which some argue are scary sharp but apt to dull more easily after damaging bone hits; at the other extreme three-edged heads like G5's one-piece Montec or laser-welded Razorcaps sharpened two edges at a time, that some argue don't offer enough sharpness. I've experienced killing results from both approaches so have no opinions.

A Lansky Sharpener or GATCO Sharpening System, with blade clamp and guide rods, gives you some ideas on the former, the latter created by pushing two edges at a time across a flat stone. The Real Deal sharpening system from Ballistic Archery/Steel Force allows you to sharpen across the blade like factory blades, while maintaining the proper angle through a rail system, edges honed with diamond file, leather strop and finishing compound, for an incredibly sharp finished job.