I would go straight to the offer because most landing pages have a high bounce rate (visitors leave without clicking through) and Facebook ads are getting more expensive by the day it seems. You want the most people to view the actual offer as possible.

Also, choose CPA offers that pay well, small "pay per lead" campaigns such as $1.60 per lead are hardly profitable on Facebook ads, you need headroom.

Hope this helps.
God bless.

I would definitely have them land on a custom fan page tab with your offer. That way, everyone will at least see your offer once. From there they can still like your page, but you get your offer in front of them first.

I would agree as well, however, what about capturing some of that traffic on FB with a newsletter opt-in box on your squeeze page? Remember: "The money is in the list because the list is money!'

The best and cheapest way (what is regarding the ads) is to land them on your fan page. You can force them to like your page by offering some incentive, that way you get a fan for life and you can promote to it as long as you want.
One way is that when they receive a gift are straight redirected to CPA offer, you can do that via a php script that you host on your server and of course this is done via FB apps (if you are newbie read some instructions about it or leave that part for later on).
The other way is like Brady Lewis said it in his post to do it on application tab and they can click from there. But you have to be careful which CPA offer are you promoting and if your landing page is that tab which directs users to CPA offer. If you are going to go that route you need to first make a fan page and create an ad. And when you are approved create custom tab and change landing page for your page from wall to your application tab. Do that change from within a page not your ad.
Hope this helped.