How do you get your clients to trust you? Trust yourself, first.
"You can't get without giving." This goes back to Napoleon Hill's "Think and Grow Rich" but also goes back through the Bible's Golden Rule to the oldest known verbal traditions.
One phrasing of it is, "Energy flows where attention goes."
There is also a unique version of it, ascribed to the Emerald Tablet - "As within, so without."
I can name off-hand at least a dozen more authors who have talked about this. The key thing is to put this to work in your own life. Any problem in attracting customers and clients to any business is whether that business owner (and every single employee in it) trusts themselves enough to give away trust.
These old principles survive and have use today as ever, because they describe natural laws which exist independent of time.
Whatever you are in yourself is what you will create around you.
Truly successful, long-standing businesses thrive, survive, and prosper because they are completely involved in the success and survival and prosperity of their clients.
To do this, they first have to let go of any type of "death wish" or self-destructive attitudes they may have been carrying around. (Like being critical of others in any form or fashion.)
Because you will create in your clients those same attitudes - or they will simply move away to no longer have to deal with that.
While some people deal with "relationship marketing" you have to know that it is all based on the point of being in a good relationship with yourself, first. You have to be at peace within as a starting point.
This is why self-improvement books continue to be popular.
Mike Dillard, self-made millionaire at age 28, ascribes this to the "alpha marketer."
Learn to trust yourself and you'll be able to trust your clients. When your clients see you trust them, they will trust you.
Treat your clients like an animal queued up for slaughter, and you'll have constant turnover in your lists, and be always expending more money to get new customers instead of servicing the existing clients.
Improve your own life and then you can help others improve theirs.
PS. I've got a ton of books at Midwest Journal Press which can get you on your way. Let me know, and I'll send you any free review copy you want of what I have.