LOTR is a fantastic game - i can normally get Destroy The Ring (by completing the 3 multiballs) most games, but have yet to finish the Fellowship multiball.
My 1st aim is to always get a mode started as soon as possible. Modes such as the Ents are great to add souls to path of the dead for Return of The King Multiball - during modes i always try and get shots that will build up for multiballs (ie: get KEEP rollover lights and lock balls on the sword). If i have a multiball ready to go, i always try and start a mode before the multiball - this way you can often complete the mode unintentionally during multiball due to the number of balls flying around - this then gets you extra gifts of elves - which might be an extra ball.
You also get an extra ball after a certain amount of tower shots (left loop to top right hole).
I try and complete the modes if possible (except witch king i find really hard), as when you get 'There and back again', which is after you have completed all the modes, you get 60 seconds to shoot the ring, and then make any lit shot to collect whatever pints you got in that mode - pretty cool feature i reckon, so more points you get for the mode- more points for there and back again.