To sound sincere you have to be sincere. Why do you only want to sound sincere?
my question as well but I answered as if he meant that he IS sincere but "comes off" as being sarcastic or apathetic and went from there; interested in his reply.
ok, I get your point, then put the word sincere into the apology. I am sincerely sorry for what happend, it won't happen again and can we forget it and continue our friendship as before? (this of course is only an example)
oops; that makes sincerity less probable. Can you "get out of yourself" a bit and let "wonder" become part of your perspective?
With wonder comes awe, with awe comes respect, with respect comes appreciation and thankfulness...sincerity (humility too) comes when we see, appreciate and speak to the beauty that we have absolutely nothing to do with...try it and let me know how it works for you.
the best way to sound sincere is to always tell the truth
Let the passion come out of you... Let your words burn out of you and even if you stutter or say "like" to much, your tone of voice will make everything sound better. Soften your voice and relax.
You must say how you feel, and mean what you say. It's that's simple. To me, it seems you hold back what your really trying to say. Once you start speaking your mind, you won't be able to stop! Give it a try :)
Perhaps you should try to fake it.