One of my favorite WP7 features is the wireless sync with Zune client. The podcasts I like get downloaded daily by Zune. Since I listen to them exclusively on the phone, I need to sync them. There are two ways to accomplish this. One is using a cable to connect the phone and the computer. Another one is using a home Wi-Fi network. The Zune client needs to be configured to use wireless sync by clicking Settings > Phone > Wireless Sync. That is all the configuration necessary to enable wireless sync. The Wi-Fi sync will not start automatically unless the following conditions have been satisfied.

• Your phone and PC are both connected to your home Wi-Fi network. Note that wireless sync is not supported on workplace Wi-Fi networks.
• Your phone battery has at least a medium-level charge ( Battery icon at medium-level) and your phone is connected to an AC power adapter (that is, your phone must be connected to the wall charger and not connected to your computer).
• You’re not interacting with your phone. For example, you’re not touching things on the screen, the backlight is off, and music and videos aren’t playing (it’s OK if a song or video is paused). 

Unfortunately there is no way to force the wireless sync. You have to connect the phone to the computer in order to force the sync.