Hi Corrie

Do a Google search on "depth of field" and there will be plenty of info, but as a rough starter guide, shallow depth of field (or shallow depth of focus) is a function of a few things that need to come together at the same time.

First you ideally need a fast lens ie. one that has a large maximum aperture (these don't come cheap) and the effect you're after is achieved by a combination of a large aperture, lens focal length, distance from you to the subject and distance from subject to background. Accurate focussing and deciding what point to focus on is obviously critical.

The longer the focal length of the lens the better - a wide angle will always give you more in focus than a telephoto for any given aperture. The more distance between your subject and the background the better, in order to give your background a better chance of going out of focus. Shoot in Aperture priority and set your aperture to the largest (smallest F-number) that your lens will allow.

There is always a bit more to it than just this, but hopefully the above will give you a good starting point. None of my business of course, but I do question the wisdom of shooting something as important as a wedding and a corporate catalogue when your knowledge-level is obviously as low as it is?

Anyway, hope this helps.

Cheers

Bob