1. Bugs. Does your venue spray bug repellent on their lawn and grassy areas? If not, and if your reception will not eventually be moved indoors, how do you plan to keep bugs away from your guests? Citronella candles? Torches in the ground? They make really cute citronella lanterns (if that's your style) that can be hung from tents, put on tables, or put into the ground. No one would even know they double as bug repellant :)
2. Cake/Cupcakes. If you are getting married in Michigan this summer (or anywhere hot for that matter), where will your cake be kept until the reception? What type of frosting will it have? Light frostings such as meringue, whipped cream, and buttercream will melt faster in the heat than something heavier such as fondant. Always double check with your baker.
3. Trash Cans. It's important to make sure trash cans are easily accessible to your guests. They should be strategically placed throughout your reception. Some more questions that revolve around trash are: Who will be responsible for emptying the trash cans? Who will supply the extra trash cans and bags? If the venue (such as someone's backyard) does not have anyone responsible for the trash, where does it go when it's full and who is responsible for that? In Michigan we recycle our cans and bottles. If you'd like to make sure those items are placed in separate bins from the trash, make sure you mark them appropriately so that all the guests know that trash goes into a different container than cans and bottles do.
4. Lighting. For two reasons: 1. Photography. 2. So guests can see where they are going. A photographer needs to have decent lighting to take pictures when it's dark. Natural light is always the best, however, a well lit tent or reception area would help them out greatly! Once the sun sets, it's important that your guests can find their way to the restrooms, their cars, the bar, wherever it is that they need to go. Lighting a pathway to take them to such places could really enhance their experience, and keep someone from twisting their ankle!
Is your reception indoors or outdoors? If it is outdoors, what are you most concerned about? If it's indoors, what's your main concern?