Currently on a clean bulk, most workouts I'd aim for 6-8, or 8-12 reps depending on the exercise.

Within those reps, whats the best way to train? Say failing at the 5th or 6th rep, with a few seconds break and then continue up to 8? Or should I be failing on 8?

If I've got a session booked in with my trainer, sometimes this person gets me to lift weights in excessive amounts, at times to the point I'm doing bursts of 3/4 reps.

Is this a sure way for muscle building or am I lacking in endurence?

I'm getting to the point were I'm no longer getting much DOMS or feeling pumped during a workout with the above method. Is it time to change?

I'm not following an exact rotating plan. Just various exercises and alternating each workout between upper and lower body 3 times a week without repeating the same exercise in the same 7 days, with about 15mins of intense cardio on the days in between (boxing on punch bag or padwork day after leg workout, running after upper body workout, + 1 rest day).

1-5 reps= strength
6-12= hypertrophy/look bigger
12-18= endurance

Find out what you want then go with the rep range you think you want..just keep adding weight to the bar and you should be ok.

Bump for newbs.