C = COMMENT
Whilst reading a post you like make and leave a comment - just something as simple as thanking them for that post, or telling them how it helped you or how you can use it. or that it was that good you shared it
L = LIKE
This is so simple - just click Like on their post... or even click on the heart if you love it that much...
A = ADD THEM AS A FRIEND
Send them a friend request and add them
M = MESSAGE THEM
Private Message the person you just added
Then introduce yourself, give them a complement and find common interest unless the person you have befriended has a similar interest - sport - dancing - films - theatre...