Have as few tags as possible and make them relevant to both your channel and video. The more you have, the less importance YouTube/Google gives each one when people search for those terms and instead looks only for large combinations of them.
Have a look through your videos and choose 3-5 key tags that you think represent your videos and what viewers can expect to see. Also choose 3-5 that represent your channel (bike brand & model, "motovlog" etc) and put them in every video too.
E.g. My global tags are "motovlog", "triumph street triple", "alps", "mountain", "lake"
Google will automatically sort out the various endings (lake/lakes etc) so don't go nuts with those like some people do as it will just make your channel less responsive to those words.
Source: YouTube official help forums.
Good luck!