“I've treated bullet holes, knife wounds, laser burns . . .” - a frustrated ship's Medic to his Captain.
“Some of our jobs are more interesting than others,” - the Captain.
The Universe of Traveller is full of danger. The mini-game that is character generation (rather than character creation) emphasizes the fact that a Traveller universe can be deadly. But what particular things are likely to kill a Traveller?
Simple answer: bullets. Most fights in Traveller are gun fights, and it takes only 2-3 bullets to end a Traveller. So avoid those. But how, you ask?
I considered this question after reading Rick Stump's blog post on Low Level Encounters in D&D. In that game, PCs at lower levels are fragile and not powerful. They tend to die a lot. Traveller PCs are not “first level”, but their experience does not make them more resistant to damage, unlike D&D. TTB has no guidance at all about how difficult any type of encounter may be. The Referee can put any obstacle in the PCs' way.
Rick identified four factors that the Referee must keep in mind to avoid creating Killer Encounters resulting in a TPK. I have nowhere near Rick's amount of experience as a Referee, so I take his ideas as a guide. Looking at the rules, these four things are what players, rather than Referees, should watch out for.