The easiest way to get a hot girl in bed is to actually be said hot girl; then, simply get into bed. Mission accomplished.

Now, assuming that one is not a hot girl, per se, the matter can be decidedly more difficult, indeed. But, of course the more important question is not how to get a hot girl in bed, but rather, why does one want a hot girl in bed? Why in bed? What does one wish to do? Would an un-hot girl suffice, or must she be truly hot, or would lukewarm or even tepid be as effective? What constitutes hot? Can such a thing be objectively determined with exactitude? What if she was not hot, but completely in love with you and absolutely devoted to your happiness and enjoyment of life?

Perhaps one should stop wasting one's time in sexual metonymy -- boiling the essence of an entire person to a single, all-important anatomical organ.

The ironical answer to the question is that one gets women from across the full temperature spectrum not by plotting and scheming silly shortcuts thereto, but rather by putting honest, mature, sincere effort into finding out what women want, and then demonstrating that one's character, personality, and ethics are able to provide for those desires. Women desire strength (ie, not physical), character, confidence, loyalty, courage (moral, not mortal), and a sense of humor... fortunate, since we men are pretty humorous.

So, the only absolutely reliable way into a woman's heart... and pants (if that's all that one cares for) is through honor, courage, character, loyalty and respect. But, for someone asking such a question, those are obviously in extremly short supply, so I must recommend roofies... or a heavy club; for someone so immature and purile, conscious women are clearly out of your league.