What exactly is an oddball planet? Opinions may vary but they fall into two types.
The planet either makes you say, "Yikes!" from orbit.
The planet makes you say, "Yikes!" after you land.
It is theoretically possible to create a planet that makes people yike from another star system but then it's deuced hard to get them to go there.
Generally worlds that make you yike from orbit have charming local features regarding the starport, lithosphere, atmosphere, hydrosphere or a mixture. Worlds that make you yike after you land have unusual features regarding the population, government, law level or tech level.
The planet is too big. Its size code is a fricking letter. For a Fat Trader making 1 gee at best this is problematical. Landing craft have a problem with these worlds as well (for some reason, even though they usually pull 2or more gees.)
Rotation is often not considered in landing maneuvers. Our world spins at 1600 kph and provides a significant boost to our primitive real world rockets. In the case of tidally locked worlds this is not the case. You have to kill all velocity to land and that's a problem if there's considerable debris in orbit. It's still whipping about real fast and could hammer a ship descending to a fixed spot.
For that matter debris in orbit can lead to something called Kessler Syndrome. You get enough bits of junk up there and they begin smacking into each other creating more bits of junk until you have a mess. this is where your anti-missile program performs double duty zapping specks of paint and old juice boxes. Planets with TL 5-7 might have been trying space out for themselves with reaction drives and polluted their near orbits before making contact with more advanced cultures.
Radiation belts are another factor. Large planets have large cores and strong magnetic fields for trapping all kinds of particles. Some planets might have magnetic effects that disrupt communications and sensors.
Finally good landing areas might be at a premium on a world with unstable, chaotic or mountainous terrain. Mudslides, brushfires, floods and tremors are all possible in wilderness areas. For that matter quakes might be a way of life in urban areas.
Once you've landed the fun is not necessarily over. A wilderness landing is the worst. A 100 displacement ton ship like a Scout masses 1000 tons. Even if it doesn't sink into the ground initially there's no guarantee it won't sink if left there for any length of time. There's also the possibility of earthquakes. You can always leave the engines running to lighten the ship by an arbitrary amount. Mind you don't set the idle to high or the ship might drift off with the breeze.
All these factors might lead to placing a starport away from other interesting areas of a planet (more on that later). Some planets might build an orbital tower or simply accept most deliveries at orbital facilities for final transport by seasoned shuttle pilots with known skills..
A few pointers for players with evil referees; consider each jump the way you would a trip to a foreign country (not one of the nice ones with espresso and poolside bars). Would you make a trip to some totalitarian tyranny without researching it first? Would you hit Australia without reading up on the most common venomous animals and football rivalries?
Use the library program when you plan your next port of call. Better yet, use it to choose your next port of call. If there are any hazards balance them against the risks and prepare for them. If anyone has TAS membership use the contacts it provides to get additional information on your next port. The same applies to Scout and Navy characters assuming they're near the right base. Also spending some money in the starport watering holes can usually turn up some information especially if a commerce line links your current port to your destination. Those rumor tables aren't necessarily just about treasure and jobs.
We've recently found a number of Super-Terrestrial planets. The old size generating formula of 2d-2 doesn't a;ways cut it. I suggest the following:
On a natural roll of '12' roll an additional die. Read the new diameter as follows:
1: Size A
2: Size B
3: Size C
4: Size D
5: Size E
6: Size F
Generating atmospheres gets a little tricky and since I'm in no way qualified to make up an original system that is realistic I'd cap the maximum size modifier at +3.
Will Shuster rightly points out that TL worlds DO rotate but their rotation period is equal to their revolution around their primary. Which is pretty darned slow in general but should be taken into account by pilots and navigator types. Thanks for keeping me honest.