Having completed 100% of the game today, I've put together another 100% checklist which will show you exactly what you need to do for full completion of GTA4: The Lost And Damned. The checklist will let you save your progress to the website, and will also generate a mini-gamercard type image showing off your completion.
Please note: If you registered an account for the GTA4 100% Checklist, you will need to register a new one for The Lost And Damned.
Lost And Damned 100% Checklist
You may also wish to check out the 100% Completion Breakdown guide for The Lost And Damned which may help you figure out which objective you're missing if you've only got a few percent left to get.