How to not have an affair.

First and foremost, do not pick someone with a physical feature you immediately dislike. Let's get real here, vamos al fuckin grano, don't lower your standards in any way. Because the last thing you want is to stand in the street, smoking a cigarette and thinking, "I couldn't even make a short man love me." But then again, don't pick a picturesque lover. Because that's what you'll be left with: pictures of their black curls mixing with the feathers of cheap down pillows, delicate tableaux of their wide unnameable blue eyes thinking of other people they wish you were. In fact, remember that a successful affair is the seduction of self. When you mount their body, consider the act an essential dance, your way of healing yourself from the lover before who made you feel less than. Note the thighs, firm and biblical, an ancient bequeathing of generations. The sharp collarbones, at once fashionable and tragic. No! Not theirs. Yours. And for gods sake, don't laugh during. Balzac said, "Happiness is the beauty of womanhood, as clothes are it's disguise." True enough, but let us not confuse this with the caustic notion that a woman without clothes is a joyful one. Put your clothes back on and smoke a cigarette, always in that order. You are tired enough after making love, so don't give this lover the opportunity to change what you smoke by rolling you a cigarette or lighting one of theirs. Even worse, to smoke their cigarette and fall asleep with a lover who deems it appropriate to hold one another in slumber. You may sleep together like sick expats in a freezing German city. Finally warm. And so easy do we mistake inertia for homecoming in these moments. Not asking you to leave does not signify the desire for your presence. 
Surely your lovemaking will reek of the primordial, for even the most gentle affair is a union o utility. Cover your nose diligently when encountering this lover's musk, all wet bark and rough salt. You will find yourself on a dank cobblestone street in Madrid, or among rotting fruits in a makeshift market, perhaps nose in a mug of steaming cider, and the irrepressible fact that you will never smell something quite like this lover again will snack on your innards like the worm in a tequila bottle. And you're in real trouble if you spray their blankets with your perfume when they aren't looking. If you're at that point, they've already won. They couldn't give half a fig about smelling you later on. 
More on this primordial state. We may be a global culture which now values convenience, but god damn does this affair remind you that we were hunter-gatherers, beings which crave steady hands and able minds. Therefore do not allow this lover to teach you a skill, particularly one which will make you feel capable or, worse yet, more poignant. They may, for instance, teach you to roll cigarettes. Congratulations, now your only respite and that yellow fragile halo on your finger pay constant tribute to a private craftsman. 
To ask a lover about past affairs is the juvenile move of a sadomasochist. You deserve whatever lashings their former lovers unassumingly whip upon your gut. The older we get, the more people there were before you who mattered more than you ever shall. The older we get, the more crowded your little DDR-issue sized bed becomes. Seal your wounded eyes, instead, with those long amorous lashes and use their pelvis for it's god-given purpose. I suppose it's best to keep any knowledge to a minimum. The first indication of a broken heart is basting trivialities with the grease of universal significance. They will have your favorite poet on their shelf and your favorite parent's favorite record. 
Never have a soundtrack. Your affair is not a grainy bildungsromanian classic that deprived fathers will watch, missing that sweet college girl they passed up for your lined and unkind mother. That song is not saying what your lover doesn't know how to. If it's true that their very fingernails ache for your tongue, those words will be said. They will be surely said. They will not follow you to Poland, they will not miss that plane, they will not look up the secret song you only listen to sobbing in the corner of the shower and then learn to play it on the guitar. Like it or not, like it or not.