Networking - How to prepare for Interpolation?

I am currently building a very simple networking game. My player moves using transform.Translate() and transform.Rotate() - but at this moment the code is so simple it can still be changed. Previously, I’ve handled this by sending key commands over the network. However, this hasn’t really taken lag and latency into account and I was wondering if there was a better way to set up packets. I know I need to send a timestamp. Should I also send the last known vectors?

Here are a couple of good resources that discuss networking for FPS type games.

https://developer.valvesoftware.com/wiki/Source_Multiplayer_Networking