Hi commander, and welcome to the world of exploring.
There is some amazing information here:
https://forums.frontier.co.uk/showthread.php?t=81653&highlight=exploration which has collated loads of useful information on exploring, well worth a read if you got a spare 15 mins.
My own personal experience is that picking the star type before hopping into a system can really pay dividends; using the info tab on the navigator page and picking systems based upon the primary star prefix. I generally try to pick worlds with primary yellow, orange or red stars; with a preference for smaller numbers after the primary classification (as any planets will be generally closer to the sun and therefore quicker to scan, so G1-K3 etc).
A useful mnemonic someone used (apologies can't remember the original author) was to avoid LOFTY suns (ie those with a classification starting with any of those letters); primarily because you are unlikely to be able to fuel scoop from them, but also because, in my experience) they don't often have interesting planets either. Further info on the basics of the classification system can be found here
http://en.wikipedia.org/wiki/Stellar_classification (Elite, bah making me learn stuff!)
Other things I've notices (albeit with a low sample size at the moment, is that stars starting with HIP then a number have a good chance of being relatively interesting systems, it's still hit and miss every new system you go into. One bit of good news though, black holes and neutron stars do show on the info tab of the navigation page. For example if you search for 13 Andromedae you'll see it has a neutron star and a black hole in the system.
Over time I've got used to what type of planets are worth going out to scan based upon their size, the star they orbit, their distance from that star and the colour of the planet on the system map. Always investigate any that are blue and green!
Happy (further) exploring.
