This game is confusing. How do you give your ships orders? I can't figure out how to send out my geological survey vessel to, y'know, survey geology, no matter where I look. This game would definitely benefit from a wiki as extensive as Dwarf Fortress's.
There's also the automated option, which works fairly well. In the Task Groups window, check the second tab. Set the default orders for your survey TG to scan system bodies (or system locations for gravsurvey ships). For most systems, you just need to send your ship into the system and it'll do everything automatically. Comets and large systems (most commonly, binary/ternary systems) occasionally leave some unsurveyed bodies since the "survey nearest foo" orders only look within a 3 billion km radius.
Default (and sometimes conditional) orders can be very useful for certain tasks. For others, not so much. Note that the "> 25m" and "< 25m" in the (un)load colonist orders actually refer to whether the population is a source or destination. Check the civilian tab of the population window for that, and be aware that small pops (< 25m) seem to automatically revert to destinations during the next time increment. Also, be very careful with automated jump gate construction, as the ship will insist on building a gate on both sides, thus exploring new systems and potentially spawning new NPRs. I suggest manual construction instead.
Fun fact: A TG with both "build jump gate" and "survey system locations" orders can, in theory, explore the whole galaxy without your intervention.