Finding materials is not that difficult under normal circumstances. One part is knowing what you're looking for and checking the system maps to see where this might be found, and getting some idea how often it might be found.
Let's talk Technetium... since I did have to put in some time in the beta looking for this*, here's my findings:
1. Once a suitable planet had been located (.8% Technetium), I had to figure out where I wanted to start looking. I picked a crater with a huge central mound. I landed on the west side of this, and started driving around. A few km out, I started picking things on my wave scanner. Outcrops mostly. These usually don't drop anything terribly interesting, but I shot them anyways. As expected, nothing interesting.
I drove on, looking and listening. Found a few Bronzites - these also rare contain anything interesting, but I shot them anyways. One dropped 1 Technetium. A short distance later, 2 Mesosoderites or w/e they are, they start with an "M". These have better chances of giving up good items. Picked up 2 Technetium from 3 maybe 4 of these. Then I hit a nice spot, in some bumpy terrain with 3 Metallic Meteorites 1, 3 and 5 Technetium from these, as Metallic Meteorite usually give up the best stuff.
2. I also tried shooting asteroids and various ring-rocks. Got a lot of everything but.
3. * from above - Technetium was missing from the beta initially, but was added back in, and did, indeed, spawn in places it was normally found.
4. If you don't find what you're looking for, or the type of rocks you need to find it in:
a. Pick a different location on the same planet, at least 5 full seconds flight time from where you were.
b. If you're on flat ground, look for a crater, ravine or valley. These often contain other kinds of rocks.
c. If you're still not finding what you're looking for, find a world with some manner of volcanic activity - be it Ice or Water geysers or Lava Spouts, and find the fields where these are occur. Around these areas you will find various "new" rocks (Piecious Cobble) as well as various Crystal formations (Crystal Fragment, Needle Crystals and Crystal Clusters). These tend to contain better items - especially Needle and Cluster formations. This has saved me countless hours of looking for odds and ends.
It rarely takes me more than 10-15 minutes of cruising around shooting rocks to find what I'm looking for on any given planet - Except Polonium... I almost never find Polonium.