There are a couple of different ways humans currently propel spacecraft, and a few near-future technologies. Somewhere in the future may also lie FTL technologies, too. As I understand it, the list of futuristic STL propulsion methods that are at least plausible are as follows:
- Ion acceleration—would this actually be feasible for something the size of a sci-fi starship?
- Nuclear power—would it be better to use fission/fusion to heat a reaction mass, or to just detonate the nuclear material behind the starship?
- Antimatter—are there any hypotheses on how we'd synthesize enough antimatter for space travel?
- Laser + solar sail
And our list of plausible FTL methods contains only:
- Alcubierre warp drive
First: are there any plausible STL or FTL methods I've missed? Second: would an alien civilization propel their starships using these methods, or should we expect them to have come up with something completely different?