hi ams,hope that you are enjoying the coarse!
dont worry about the bidding,some people from crewing/scheduling should come in at some point on your coarse and tell you all you need to know,then its just trial and error for a few months till you find a way of bidding that suits you!
and dont worry about getting left with the less popular flights,at heathrow the distribution of flights is not done on seniority so you will have as much chance of getting what you bid for as someone who has been there for 25 years..its all swings and roundabouts!
good luck,see you on-line soon!