Hello!
I had to post a comment here, cause I've found a great website for checking our pronunciation, it's the best I've seen so far:
http://www.uiowa.edu/~acadtech/phonetics/#
Just choose 'American English', then you click in consonants: manner/ Liquid. There you'll see r and l distinguished in a video and graphic, with examples and everything you need really.. it's an awesome site. Have fun!