I am sure all the regulars know how this works so am writing this more for the newbies.
Before I add someone to my trust list I check out many things. First of all is to read some of their reviews of course. If I find them highly useful or useful that is a plus.
I check to see when they became a member and when the last time they wrote a review is. If they have not written a review in over 6 months I do not add them, or if they have written no reviews at all because how can you know you trust someone if they have not written anything?
I check to see if they read and rate others and if they leave comments.
Mouthshut notifies me when someone on my trust list has added another person to theirs and I always check these out.
I read many from the latest 30 list that are new to me and people who have rated others. I check out many people and add several a week to my trust list.
It is a nice gesture when someone adds you to their trust list to send them an e-mail and thank them and to read some of theirs and add them to your list. That is not to say I add everyone that adds me but more often than not I do.
Once on your trust list you should set your alerts to let you know when they write something new so that you can keep up with them.
Basically dont add someone just because they add you unless you enjoy their reviews. Once added read everything they write and try to leave comments when time permits.
As I said I take many things into consideration. Each person may have different ways for deciding to trust someone but a trusted circle is a must if you want to get your reviews read and reading others is a must also.
Little note here I have not been here much the last couple of weeks due to some problems but have read all my alerts and rated, just havent had much time to write or to leave comments.