Here are a few general answers.
It depend on what type of amulet you are wearing. Different types of amulets had different purposes in protecting the wearer, and have to be wear differently, the following is some general view.
All Buddha images should always wear higher than the waist level as a mark of respect. This including Takrut that has a Buddha image on it, even if the image
cannot be seen clearly because of the nature of the Takrut talisman. (Takrut
are mystical yantras inscriptions written on gold, silver or bronze foil sheet,
and rolled up in a tube form which one blessed by the monks).
Traditionally, Phra Rahu amulets are wear at the back of our body. Some people
say it is because he can protect the attackers from harming you from your back and drive away black magic.
Let’s say for example, Phra Ngang is allowed to be put inside your trouser pockets. But not all amulets can be act the same. If you have no idea about it, it’s better for
you to get the information's from seller, temple or the master who create it.