Advice needed on filming

Hi all.. I have just started using my 5d mark ii for video and would like some advice from the pros!

What's the best way to focus? Manual?

Ideal shutter speed? So far I'm using 1/60

What to do if it's to dark? I usually use my 24-105 and the f4 is quite limiting.. What's the highest ISO I should go too?

Manual is the only real way to focus whilst shooting video, you can use AF when setting up a shot, but for changes while shooting manual is the only realistic method. As regards shutter speed the 180 degree rule, ie if 30fps then 1/60 if 60 fps then 1/125 Try and keep the ISO as low as possible though 1600 should still give you decent shots.

My personal opinion always focus manually with that method you know what your getting.you don't want to come back to edit and find out your subject is too soft or out of focus. As for shutter speeds it depends what you want. 24 fps is more of the cinematic feel and what i always film in, 30fps i believe is more of the normal standard and documentary feel and 60 fps tends to look odd but if you wanted to have a scene in slowmotion it's best to have as many fps as you can get and for DSLR's the most we have at the moment is 60. last is if it's too dark A. either invest in some soft boxes "continuous lighting" i got a 3 light set up for around $200.00 online or B. adapt to your location and use what available lighting you have lamps street lights etc. ISO like artyman said keep it low as possible the higher you get the higher probability you'll have noise and grain in your footage. But honestly the best thing you can do is trial and error practice! it's just like anything else. through failure you gain experience and knowledge of how not! to do it lol gets you closer to what you want to achieve.

Get a used 50mm 1.8 for 80$ It will be well worth it!