Familiarize yourself with the language, indigenous slang, and political situation.
Learn how to perfect the local accent.
Familiarize yourself with the political structure and local beliefs.
Attempts to alter history very rarely end well.
Do not arrange things so that your ancestors do not meet. Do not kill your ancestors. Do not fall in love with your ancestors. Avoid your ancestors entirely.
People who bear a strange resemblance to you, your family members, your significant other, or anyone else you know are to be avoided.
While it is possible to capitalize on information from the future, doing so is generally considered bad form.
Avoid conversing with psychics, for you will confuse them greatly, which is just mean. Also, you risk being found out.
Do not import technology from your own era. This includes weapons, communications systems, electronics, etc.
It is understandably tempting to try to approach famous historical figures. This, however, should be avoided, because no matter what you do, you will become involved in an undesirable situation.
Do not incite the local peasantry (or the equivalent) to rebellion. EVER.
Trying to tell the locals what their future holds never ends well.
Avoid monarchs, chieftains, and all other authority figures. You will either be seen as a god-send to help the ruler or a satanic demon from beyond. The first situation will inevitably result in the Treacherous Plotters deciding they have to kill you. I?m sure we can all figure out what will happen in the second instance.
?Tis better to be thought a lunatic than a psychic, saint, sorcerer, demon, or what have you, in that order. All of the above are preferable to being found out as a time-traveler.
Time travel and homicidal psychopaths should not mix.
Never, under any circumstances, allow any indigenents, especially children, to play with your time-travel technology.