For getting a new WiFi connection, you could try at the command prompt ipconfig/release ( to release the lease to the WiFi adapter and access point or bridge), then enter ipconfig/renew ( grab a new lease from a different DHCP connection with a gateway or same lease as the prior DHCP connection.)
Sometimes I also have to flush my DNS by using ipconfig/flushdns
All commands can be seen at ipconfig/? command
ALSO... If you disable and reenable your WiFi adapter via the switch on your laptop, usually a slide switch if it has one, you can also force a connection release and renew....
You can also go into the wireless preferences configuration and specific connection priorities, if you want one connecton to connect first over another of available...
Hope this helps .... Dave