Edited: Nigel, your remark is not completely correct.
There are trams direct to the centre of Gent (Zentrum or Korenmarkt) from both Gent stations.
There are only trams from Sint-Pieters railway station in G(h)ent, not from Dampoort, the other station. There are indeed trams direct to the centre and Korenmarkt is one of the stops there, but never heard of Centrum. Maybe it counts for buses, but as far as I know not for trams in Ghent.
jaimeelsabio - Indeed all trains from Brussels arrive in Ghent at Sint-Pieters. Trams from there to the centre are very frequent. Usually you have to take line 1 to Evergem or Wondelgem and every stop is anounced, Korenmarkt and Gravensteen are good stops for getting out. Bus lines have other numbers. For going back you have to take trams of line 1 too but with direction Flanders Expo, clearly visible from the outside above the driver seat. It works in the same way as the metro in Paris, the lines have numbers and the names of the final stops at both ends. Looking at the website of tram and bus operator “De Lijn” I see that the trams of line 1 don’t stop in the centre anymore but think only for this month, hopefully this is temporarily. Trams of line 4 call at Korenmarkt too, but ask to be sure.
Single tickets costs €2.50 and a 10-ride ticket is yours for €17,-. Traveling with two you can have 5 rides with the latter, within each ride you are aloud to change lines but within 1 hour maximum. A selling point is the “Lijnwinkel” in Sint-Pieters railway station, also the place for up-to-date info about the tram, bus and tickets. Brussels has another operator so these tickets are not valid there.
If you have no mobility issues it’s an easy walk from the train station in Bruges to the historic centre. It begins as soon as you cross the busy road just outside the station. From the main square you can take the bus back if needed.