Sometimes being there is more than enough. To let them know that they aren't alone. That you care enough to stay by them even at their low times.

A good friend lost her baby last year to SIDS. I've never had kids and truly did not know what to say. So I simply told her that. I told her I have no clue what you are going through but I'm here for you. She told me later that it meant the world to her. She said even family members withdrew from her because they didn't know what to say. She said she'd never felt so alone and when she most needed people they left because they didn't know what to do.

So just be there for your friend. You might not have advice but you can listen and be there for them.