1. Ensuring the control plane, ie. the BGP VPNv4 tables, look good, meaning you're receiving BGP routes. If you're not, then check to make sure you have next-hop-self enabled where appropriate and that you are not filtering route-targets by default on certain BGP-ASBR routers
2. Once the routes appear on the CEs, ping, if ping fails, then check step by step LDP and make sure labels are assigned for the destinations. A common mistake, if you have a loopback configured but not in IGP then you're LDP peering won't come up since it'll use the loopback as it's ID but the peers won't have reachability to it (unless you put it in IGP).