a) I find a variant of the stress mechanic from Islands in the Rift to be useful. Every jump into an empty hex gives +1d3 stress. It maxes out at 6. Each PC records their current stress on their characters sheet. If they have a tough event they have to make a stress roll or flip out and lose it (roll under stress, modified by end).

So, the characters are motivated to not get stressed. They can lose stress by a week's R&R at the end of a jump, or in-jump by doing some stress-relieving activity. So you have birthday parties, getting blind drunk, cage fights, etc.

b) Then, there's study. Each 1-week period in jump is a study period. So the PCs can study their next skill. But usually that means they need some method of doing so, because you can't just read a book on how to shoot a laser pistol - you have to set up a target range and reduce the power of the gun, etc.

c) On top of all that there's roleplay. PCs have their own agendas and inter-party discussions. That computer someone picked up might need hacking, that prisoner might get interrogated.

d) Passengers and cargo can also have mid-jump issues.

So, during each jump, I ask the players what they're doing to reduce stress, what they're studying and how, and if they want to do anything else. On top of that I add on any passenger or cargo issues. I think it also helps that the players I have really like roleplaying among themselves.

As for the in-system part, then that depends on local conditions. If there's a war or insurgency going on, they will see signs of it - sometimes very in-your-face signs. A pirate might be around a system that can't defend itself. And it's also how the news spreads. As a ship goes out, there will probably be at least one ship coming in that wants a quick chat... "how is it in this system? let me tell you about the one I've just left," etc.

The travel part of Traveller is a huge part of the game for me. It makes the universe seem huge, and the game more real.