Tips/Tricks on how to help friends climb?

So I'm about to hit Plat but I have a friend who I like to play with still in low silver, and unfortunately if I go Plat I can't duo in ranked with him anymore unless I get another account.

We duoed through our placements so I started this season Silver 5 and he started high Bronze so we duoed together for awhile and he got into silver 5 and I made it to Silver 3 so things were going well, and for some reason we stopped playing together and went SoloQ, but now everytime we duo we get the worst luck so end up losing most of our games together.

He's not a bad player, imo he can play at a Gold level (has high game knowledge but sometimes can make some bad plays) but for some reason the duoing isn't working out anymore. It's like matchmaker knows we are duo so gives us the worst possible teammates to play with.

So I'm wondering how can I help my buddy climb out of Elo Hell and how do we work better as a team?

http://team-dignitas.net/uploads/tinymce/images/lol_elo_hell_out.png