1. I'm constantly having problems with the investigation part of my games. Having the whole city to go looking for information seems to be to big for my players and they constantly lack ideas for finding clues.
The wizard in the party sometimes figures out ways to use his thaumaturgy to find clues but the ninja-detective-werecat character has problems using her skills to her advantage.
Another problem for me is that i'm bad at helping them figuring it out. How should i give them clues without going "yeah you just need to go to this place over there and you will find everything" - that would be boring.
I have no idea how they will try to find info so it's hard for me to plan that or to even know how they could get that info.
I have run good "hey, that's the problem" sessions and good action ones, it's that legwork and detective thing that troubles me.

I recommend the players have an in-character discussion on what they want/need to investigate and how they should go about it.  This will make you aware of the general direction and tactics they are thinking of using.  Since you'll know their overall gameplan you can see what cracks need to be filled so that your plot is revealed within the general gameplan framework that they provided.

The other general piece of advice for an investigation campaign is to make sure that the investigation continues forward with each session.  As a player in an investigating campaign there's nothing more frustrating to me than coming up with no clues.  And to tie it in with that first recommendation, if you know my gameplan you should be able to plan out spots to give clues so it feels natural.

My last piece of advice is purely my preference but I hate getting information simply on an Investigation or Contacts roll.  It feels like I didn't use any creativity or brainpower to earn those clues.  If the clues I find are worked in more organically I feel a sense of accomplishment and enjoy the investigative campaign much more.

2. I'm lazy. I'm constantly underprepared and have to run a lot of stuff on improv. That's okay for me but the game is lacking because of that. Any tips for GMs that don't like to plan that much ?

This sort of applies to #1 as well but our GM often asks for an idea what our characters plan to do in the upcoming session.  The players are by no means required to stick to that plan but having an intended plan helps the GM focus on what material to prepare and how to make sure another step to the investigation is made.

So if you ask us what we want to do this week and we tell you we want our characters to investigate the Shady Nightclub, you can focus your preparation efforts into the Nightclub, the NPCs who should be there, the clues that you're going to give away there, and how the clues can/will be revealed.  Maybe we will get distracted and not end up at the Nightclub but if we stick to the plan you have a well-prepared session without having to break your back.

That said, the worst campaigns I've played in were terrible because the GMs did not put effort into preparing their games and often the sessions were improvised and thrown together at the last minute.  My initial reaction to your comments about being "constantly underprepared" and the "game is lacking because of that", was that if you're unwilling or unable to put the proper preparation into the game that you should step aside for a GM that is willing or able to put in the effort.  And I'm sure that some GMs can improv perfectly and run an excellent game with no preparation.  But in my experience as a player I was interested in playing in a new game with a GM who would prepared well than continuing in a game where the unprepared GM found ways to mitigate their lack of preparation.

My backup character is a WCV rock star that is Elvis incognito.

It's pretty much the second one.  The sponsor can offer sponsor debt for things in line with the sponsor's agenda, or even just things not strongly against the agenda if getting the caster into more debt fits well into that agenda.

Cool, thanks for the insight.  I like this option better because it'll make for more interesting troubles for the characters than simply not having access to the magic.  And troubles always make for a better story!

If you're a GM, how often to you compel a player's aspects in one session?  Or if you're a player, how often do your aspects get compelled in one session?

I'm curious to see where our fledgling group stands in terms of compels--whether we need to ramp it up or if they're about right.  I would say our GM tries to compel our aspects about 1-2 times per session.

Ah, cool.  Thanks for all of the replies!  It's reassuring that I wasn't imagining things.  This time...

If you can pull off subtle, great, go for it, but I've found that the unsubtle NPCs are the ones that stick with them.

I think that's a very good point for roleplaying in general.  It's easy for someone on either side of the screen to have their characters be so subtle that their personality or intent gets missed by the others at the table.  I wouldn't go so far as caricature or farce but you shouldn't be so subtle that no one is picking up what you're dropping.

And that probably impacts social encounters as well.  If your character makes a very subtle inference that everyone misses you wouldn't know it should be a social attack.