For a first stopmotion film, I would take it slow.
I made the mistake of jumping into something huge with my first go at it, and it turned into a sloppy mess. I would start off with a quick battle or two if you want to go in the direction of Godzilla. In addition, start off with some generally "non-crazy" monsters. For instance, Ghidorah and Biollante would be poor starting monsters; his heads and her tentacle vines are a nightmare to animate. Godzilla, Spacegodzilla, Rodan, Mechagodzilla, and MOGUERA would be better starters. Gigan, Mothra, and Battra somewhere in the middle.
And some pro tips:
1. Always make sure your camera is steady and locked down. Nothing ruins a stopmotion reel worse than a jumpy camera.
?2. If you can, hook up your camera to your computer and take pictures through that. Not only will you be able to look back at photos with ease, but you won't have to touch the camera at all, eliminating any average chance of camera jolts.
3. Enough is never enough when it comes to photos and how many "in-between" shots you take. Don't be generous with posing, but be generous with taking photos, only moving the figure or any of its desired parts half a centimeter or so and taking the picture. You can eliminate unwanted frames later in editing.
4. The best frame rates to work with in stopmotion are 15fps and 24fps, at least for the average user. Big movie industries might go higher to, say, 30fps, but 15 or 24 will get by just fine.
5. Never use the sun as a light source. Always find a set that is lit at the same brightness 24/7. This eliminates light flicker in the final product.
6. Be mindful of what you're wearing and where you are in the room; your presence can sometimes be felt. For instance, if you are wearing red, that sometimes is reflected onto the set, giving everything a red hue. It's best to wear all black on the day of filming, as that color absorbs light rather than reflect it.
Also, shiny surfaces can reflect your image as well as the camera's. Be sure to be extra careful in your own position and the camera's security when dealing with those types of surfaces. Otherwise, the final product will see blobs jumping about the shiny area.
7. (And one of the most important) Be gentle. If the monster is moved too much from the current position, it'll take some serious efforts to duplicate its last pose to perfection. NEVER pick up a figure to change its pose, ALWAYS be careful when moving a part, and ALWAYS plan out the action BEFORE you film it. That way, you know what the figure is going to do, how fast it's going to do it, and where/how it's going to end up.
Hope I helped. =)
