Well... you gotta realise that faving, watching and commenting on every single artwork doesn't necessarily make you a good friend. It just shows you care about the person's artwork.

If you care for the /person/ themselves, then it makes a whole lot more of a difference. Invite them on Skype /Kik/Facebook/whatever and maintain contact through chat. You could also comment on their journals of advice-seeking or similar ones (those journals which ask for help, basically) and hey! If you really wanna do something nice for them, draw them some gift art/compose some gift music!

But remember, don't do these things just for the sake of it. You have to genuinely care about the person and their reactions, or what they have to say. Sincere friends are hard to come about, but if you find they're doing the same for you, out of genuine kindness/compassion, you've landed yourself a true friend! ^^

I hope I didn't just blatantly spell out the obvious, but this is sorta my way of doing things. Your preferred way may be slightly different :P