There are several photography-specific things to consider when selecting outside venues for the different parts of your wedding:

1. Weather is fickle and it is a good idea to select as many inside locations as you have outside locations (i.e. make a Plan B with inside locations).
2. Visit the location in the same season and at the same time of day as when you plan to have the photos taken, in order to gauge how your photos will look.  While the time of day is obvious, the season is also important – as we all know, the light at 5pm in summer (lots of it, plenty of hours of daylight left) is completely different to the light at 5pm in winter (the sun has already set)!
3. The best time for outdoor photography is in the early morning or starting around 2 hours before sunset.  These are known as the “golden hours”.  Think about trying to arrange your wedding day schedule so that your photography sessions fall during these times.  You may want to consider arranging a “first look” or “first sight” moment or a  post-wedding “trash the dress” shoot to make this easier.
4. If your bridal portraits will be taken outside of the golden hours (e.g. late morning, midday or early afternoon), make sure that there is plenty of solid shade available (e.g. shadows from a large tree, the lee of a building).  Strong sunlight is not very flattering in photographs, but shade softens the light and allows the photographer to capture great photos – even at midday.  Avoid dappled shade (alternating sun and shade) at all costs!
5. Some locations (in particular, places like Botanical Gardens) may have photography restrictions.  You should inquire and arrange permission to photograph in these places before setting your heart on the location.