Backyard weddings are fun and casual affairs, but can require as much or even more planning than fancy hotel reception wedding. Have you thought about these things?
You need at least one toilet for every fifty people. However, you may need extra bathrooms if the event is especially long. If your home has enough toilets to accommodate the guests, also be sure to stockpile on toilet paper, soap, and paper towels.
Check if your neighborhood requires a permit to throw a bash. If the wedding continues into the evening, consider informing your neighbors with a delivered letter summing up when and where the wedding will be and leaving contact information if they have questions.
If you plan to have a band perform, you'll also have to check if you have enough power for them.
Most caterers will still do some cooking on site. Work with your caterer to see what they need from your kitchen. If you're making the food -- congrats --, but the real tough part is making sure a steady stream is able to travel from the kitchen to the guests.
If you're hosting a large event, your neighbors will be less than pleased to find the other block taken up by strange cars. You may be able to rent parking space nearby and either use public transportation or hiring cars to transport your guests.
Bad weather is a problem for every event, weather or otherwise. A back up plan is key.