I know it's already been asked, but there really are different strategies based on the number of players.
As mentioned before, rushing the main activity line helps no matter how many players you have. Once your are a few spaces from the end of the track, start accumulating life tokens, healing corruption, and drawing cards. Put on the ring on every board to skip unwanted spaces or to end the board early. It's not always possible, but try to have Sam as the ringbearer in Mordor.
In a two-player game, cards are your biggest concern. Tip: don't "waste" too many turns only playing one card (usually because you're short of grey cards). Instead draw two and hope for a better play next turn. Call Gandalf as much as possible. Try to have Sam land on all of the black squares. Try to save the Belt and Mithril Shirt until you reach the final space (60).
In a five-player game, you won't have enough life tokens for everyone to survive each board unscathed. Also, you're runes will be too spread out to call Gandalf much. You will not have any card shortages with five players though.
I find three-player to be the most balanced regarding cards, runes, and life tokens. If you have more than three players in your family, just play with three and have the others cheer them on! Once your family has won, then try a different number of players.