Spending proper time developing your shield is a good recommendation as well, you should be able to sweep it over yourself on short notice if necessary, and you can also enchant an amulet to perform the function of a mind-shield on a more regular basis
Avoid touch. Avoid significant eye contact. And avoid conversation with said person about topics you are passionate about.
The first two are fairly obvious, the last would be like the difference between talking about the weather vs. talking about something, a topic or experience, which you have strong emotions about (positive or negative either way).
Mainly I'm talking about real-time conversation (face to face, on phone, or internet chat with or without video). Delayed comms like forum posts or letters, are a much lower risk, since your thoughts themselves are long since dissipated by the time the text is read. Retro-active mind reading is a wildly more difficult thing than real-time.
Bear in mind though, that those experienced in reading people (telepathically or via more mundane means) can potentially pick things up which you don't intend to communicate, and/or generally have experience with how the mind works on a fairly deep level which can make thought patterns easier to decipher (even from something like a delayed comm).
For example, I can easily infer that you feel very defensive about your privacy, and that you are concerned about it due to some specific thing which you very much want to keep private. I would imagine that in a live conversation it wouldn't be that hard to draw it out of you. And I can say that those who do read people tend to be drawn to such things as your desire for secrecy, since it's like a puzzle to figure out, a treasure hunt. And the prize is the buried time capsule which is your secrets... generally not valuable or important, but potentially interesting. Most human thoughts aren't that interesting, so there's an 'allure' to secrecy.
PS: Of course, if you want to make genuine friends, and have healthy relationships, you need to open up. A fortress is also a prison.
PPS: Bear in mind that whatever it is that vexes you so, it's probably quite commonplace, in this sea of imperfect beings we live in. And sometimes sharing can be cathartic, even if it's something very private.