Once the transaction is complete, the buyer is not obliged to come back - what are some good tactics to get the seller to come back to rate the transaction?
Depending on which marketplace you're talking about, but I know that Amazon doesn't want you to solicit any of their buyers since they already do it for you. On eBay, you can usually ask for feedback.
A tactic I've used is to include a reminder note within the package or packing slip that reminds the buyer how important feedback is for you and the marketplace.
I don't recommending using any software to request feedback because it's looked down upon by marketplaces is general.
Hope this helps