The basic options for a 6-man group are familiar to most of you, namely
RRRRRB - Hew the Stone
RRRRRG - Roll the Drum

Positive thing about these is the relative easiness to execute, everyone just presses red and then one pre-assigned person (usually the minstrel) chooses the last one, based on what the fellowship needs at the time. Negative side on these is the fact that a partial conjunction just does the damage, but no other benefits. And if you're, let's say, in the middle of a group of elites, you'd really want others effects too than the big damage to one elite, who might already be low on morale.

Also very popular choises are
GRRRRB - March of the Ents
GYYYYB - Chill of Bone

Really effective conjunctions. Do huge damage, rally and energize at the same time. The yellow version is for elite masters and such. The damage is bigger, but it's over time. These do have a negative side, partial conjunction is really weak.

I was just with a group that tried to do
BRGYBR - Wings of the Windlord

We had dozens of tries on this, succeeded once. The effect was spectacular, and it can really make a difference in a tough fight. This particular one summons 2 oathbreakers to help you (among other effects). Negative side is obvious, all six length straight conjunctions are really hard to execute. Everyone has to have their own pre-assigned icon. BUT, there was one positive side that I hadn't realized before. Even partial conjunctions have great effects. Even if you get the first 3 right, the effect is decent. 4 length is better, and the 5 length summons one oathbreaker. Although, if someone presses a wrong icon (or the right icon at the wrong time) in the middle of the conjunction, the effects go down signifigantly. Try these sometimes, just for kicks.

If you want to keep the fellowship at full strength, go with
GGGBBB

You're healed, and the more people succeed to press the icon in time (surprisingly difficult, it seems), the more power you get.

Some views on the subject:
Conjunction Junction

I must admit that I havn't seen many fellowship manouvers yet, probably due to random groups at my level (30'ish) not caring much for such. Thus, I usually selected what I - from the view of tanking - required most, e.g. green for health, or if I am in perfect condition, red for some extra damage.

I am most interested in the named "BRGYBR - Wings of the Windlord" conjunction, and would like to know if the exact order of colors is required or if it's just the general amount of each color that counts.

We had moderate success in Dol Dinen yesterday with March of the Ents. For some unfathomable reason fellowship manoeuvres seen really difficult to execute. I mean, some times you're stunned, sometimes you're far away from the mob, sometimes the icon doesn't stick for some reason, but none of the reasons explain why some people insist on pressing their icon TOO EARLY.