CPR, you silly naive girl.
Do you really think I would ever let myself get caught with murder?
No, your average killer has absolutely no idea of how to properly dispose of bodies, not to mention how to leave no evidence of the deed.
Once you have found your target, you take them down in a spot where there are no observers of any sort. You imeaditely grab the body, place some material over whatever wound was created in killing them, [or not if you taser them or such] place them in a double bagged garbage bag, put them in your vehicle, and return to your already setup disposal in some out of the way place. Firstly, this place should not have anyone come look around for at least a few days, but preferably weeks, and optimisticly months.
You should make sure there is running water in this location. You take the clothes off the body, dispose of them properly [burn them in an aerated mixture] and then place the body in a tub or the like, something immune to corrosion by all but the most potent of basic/acidic substances. Fill the tub with a basic substance like drano to disolve away everything but the high concentrations of calcium [bones] and then flush out the drano and replace with an acid. Voila, you have now removed all evidence of your murder, assuming you where intelligent enough to not get caught in the act of killing the person. [Pretty damned difficult to do if your smarter than a crackhead, you'd only need 2 minutes to kill the person and get them out of site, then another two or three minutes to throw some acid/base over any gore if you killed them messily]