I have a Micromax A110 Canvas 2 device with Android ICS 4.0. A few day ago, the Google Play Store app updated automatically with a new look. After a week I updated my device with Jelly Bean 4.1. So I got the Play Store with an older look (without an update). I was hoping for an auto update. But even after two days, the Play Store remains without an update. So how can I update the Play Store myself?
Usually, Google Play Services will always run in the background and if there is an latest release of the Play Store is available, it would updated automatically.
You may enable Google Auto Sync and check whether it works. If not, there may be some problem with Google Play Services. Alternatively, try installing the apk from XDA.
You could go into the Applications option in Settings, and clear the data from the Play Store app, uninstall updates (if that's an option), stop it running etc. Then go and enter the store as usual, which should force it to check and update. This might take a minute or so.