subscribe to a podcast without downloading the files?

I don't think so. Never tried.

The point of subscribing is to get the newest episodes automatically instead of having to select and download the episode.

I just do audio podcasts under iTunes 7. There you can set a preference in the iTunes Preferences > Podcast menu to not download podcasts unless you click on a "get" button next to the podcast. itunes still checks with the podcast provider and provides a summary of the podcast but doesn't actually download the file unless I get it.

I'm actually a little confused by your question. When I subscribe to a new podcast (audio or video) it will download the newest show but won't download any other shows unless I specifically "get" those shows.

Are all of the shows automatically download once your subscribe to a podcast?

I think the OP is probably saying that he doesn't want every new episode, just those he's decided he wants by looking at the info on it as it arrives. Subscribing isn't set up to allow this. The best solution is to follow the link to the podcast's website - in many cases you can download from there.

Alternatively, find the URL of the podcast. It should be on the website, or you can subscribe in iTunes, go to the Podcast section in the sidebar, click on the podcast (not an episode), click on the 'i' button at right, and the pane which opens will show the feed URL (you will have to type it out, unfortunately you can't copy it).

Then enter the URL into a browser - FireFox is best here. This will display the episodes and you can control-click the links to download individual episodes.