1) Know your assembly
You'd be amazed by the things engineers don't know about the project they are working on. Depending on the method of attachment, key criteria may include clamping pressure, die curvature, lid surface variation, alignment tolerance, burn-in temperature and time, as well as x and y dimensions of the interface. Do you know the junction temperature your device maintains during operation? A better question may be 'Do you know the junction temperature your device maintains after 2 years of operation?'
2) Know your alloy
Although indium and Au/Sn aren't throw-away materials, I advise getting to know the alloy you'll be working with. If a picture is worth a thousand words, a reflow is worth at least two thousand. Before you even start setting up a new solder process, it is a good idea to find a hotplate, some various surface finishes, and whatever flux/alloy system that will be used. It might sound non-productive, but I assure you that you will learn valuable traits of your materials if you just take some time and play.
3) Know your options
Even if you are planning on running the same assembly process for the next 5 years, you should be aware of the other possible processes. You may be able to take a couple assembly tricks from a different process to improve your existing process. Not all processes for thermal assembly require new materials, it's very possible to decrease your thermal resistance and reduce the amount of steps in assembly while not increasing material cost. I know that sounds a little vague – but that's what Technical Support is for. Let us help you improve your application!