Obviously the best travel advice you can get for taking the eurostar is forget it. But if you really insist or you just curious about having the experience then read on. First you have to be aware of the obvious no go times of the year, these are summer and christmas period. On theses weeks you can expect cancelled trains, delays of 2+ hours, the que just to get to the entrance ofthe eurostar, not the check in, just the entrance will be longer than a concert at your favorite singer. There are always the other guys in the que also, you know the people who are trying to carry more than what they can actually carry, only to be turned back because they have too much luggage, yes it happens, if you have too much luggage your ass is being turned away. two bags max, big or small doesnt matter.
If you really insist on traveling in those periods, buy the business class, check in is much much easier, however delays remain the same as you all get the same train.
Dont get the economy seats, if someone goes to the toilet and does a stinky poo, you gonna smell it for the next few hours!
Good luck!
