Because we already covered the basics of Paradoxes by Action, we will now focus on abstinence. And by that we mean both abstain from changing the past and also from having sex.
As indicated by the knowledge you should have acquired by now (if not why are you even reading this?), the best way to avoid a paradox by action is by not going to the past. But if you are going to the past, the next best way to avoid a paradox is by not going to your own past. If you are in a timeline already altered by the effects of time travel, be careful not to cause a Paradox by Inaction. If you already are in your own past, or are forced to go there by fate, destiny, or a high stakes game of Truth or Dare, do not, under any circumstances, become romantically involved with an ancestor or family member (what are you, a Nobel Prize-winning theoretical physicist?).
If Martin McFly has taught us anything - and he has taught us plenty, and not just about life preserver fashions - it's that your mom may have been, at one time, pretty hot. And if that version of your mom were to meet you, in a gross, drippy, Oedipal, Freudian twist, she might find you to be "baby daddy" material. Scientifically speaking, it may be merely the maternal instinct of your mother unconsciously recognizing her own genes. But as a horny teenager, she could hardly know the difference.
In the film version of McFly's first foray into paradoxical danger (which is admittedly totally unreliable), Back to the Future, the longer he is in the past, the more he is forced to avoid the sexual advances of his hormone-crazed mother. And the closer he gets to accidentally displacing his father, the more radically he alters the future.
McFly's failure gauge in this instance, which you'll never have, is a family photo from his present that he happens to have with him in the past. As the threads of his family history unravel, McFly's brother, sister, and even Marty himself, begin to fade from the photograph. This is undoubtedly the one fatal flaw presented by the film adaption of the tale: Flame Prince Finn is here to tell you that the wrath of spacetime is much more swift and violent than casual erasure form a Polariod picture, and its fabric is never meant to be shaken. It is of utmost importance (and sickening for the writers to have to point out) that you do not entertain such parental advances, romantic or sexual.
To put it in another way: If you in any way prevent the meeting of your parents or the consummation of their relationship in the form of exchaning bodily fluids, it could mean the instant erasure of your existance, which could, inturn, implode the universe. Additionally, it's gross.
But fear not. Well, fear a great deal - but also hope some. There is a slight chance, as in the case of young Martin, that some wiggle room exists. McFly's efforts to rectifiy everything that was changed by his presence in the past doesn't exactly "fix" the timeline - but McFly still makes the important parts work. This is known as Marty McFly's Close Enough Axiom. He is even lucky enough (which you won't be) to improve on a few things. His father, for example, now has testicles. And his father's enemy now washes his father's car.
So if you mess up the past - whether it's by killing an ancestor, stomping on a prehistoric bug, or having unprotected intercourse with your mom - you'll have to fix it yourself. Or at least get reasonably close in your attempt. All it takes is alittle elbow grease, some luck, and a hoverboard. You also may require a ad scientist, Chuck Berry, a sheepdog, and a sleeveless coat/vest. That should about cover anything that comes up.