I agree with directorix.
However, there is another way in.
If you try to cast someone who is curently "Hot" in Hollywood, they are going to be fending off offers from large money, studio backed projects and you'd have to have seriously good personal connection into them, in order to get past their agent, who realising that they have a short shelf life will want to earn the big bucks, whilst they are on the table.
However, there are hundreds of name Hollywood actors, who right at this very moment can't even get arrested in LA. If you've got a great script, a project that will reintroduce or reinvent them, you have a very good chance of being taken seriously, even if you haven't got all your funding in place.
The trick with this is knowing who to approach.
The other group of names who will talk to poor old indies are mid to high profile TV actors who are having problems making the breakthrough into film. Again, the project has to have good Arthouse credibility and will show them off as "serious" actors. If you think you have a Palm D'or credibile film, you can open all kinds of doors. However, the best place to make those kinds of deals is in person, at Cannes.
Personally, I think it's a mistake to go for a currently Hollywood "Hot" actor, you'll never compete with studio money and someone who is hot needs to earn as much as possible right now, just in case the offers go away. They can't afford to take a shot a a film that doesn't already have serious money in place. Indie films always do best, in my opinion when they re-discover old stars and bring new talent to the front.
I've made my first feature with complete unknowns, and my for second I'm using names who are very big in the genre I'm working in. I'm sure that I never could have attracted the talent that I've got for the second film, if this had been my first feature. It's all about credibility. As it is, even if I could pick anyone from the current Hollywood Hot list for the second feature, I'd still go with the people I'm currently talking to.
However, I already know that for the third film I'll need at least one Hollywood A list actor, but, I also know that the commercial sucess of the second film, the quality of the third script and my already established LA connections with the agent I need to talk to, will get me all of those things. The point is, my game plan for getting that actor on board, is already two years long.
Sucess as an indie is about understanding the business, knowing your place in it, your strenghts and your weaknesses and having a long term business strategy and by long term, I'd say, knowing what you are going to do and how you are going to do it, for at least five years into the future.