Alright. Easy.
With an openings-move, you always have to to use three basic things in your move to make it successful.
First attack: Imbalance.
Why is this important? It leaves the opponent open against another attack, while at the same time he can't use this against you. Say for example I were to shoot a fireball at you in the first jutsu of my first move. You would just send a higher rank or same rank water at me, which would defend you from it and would put me in a defensive position. Not smart.
Instead, what if you use World Shaking, or the A-rank Earth moving core, or simply a genjutsu or the swamp of the underworld technique (you haven't learned this yet). I would have to find a way to stop or disrupt the tremor or genjutsu, or movement in the earth, causing me to have a hard time and at the same time giving you another opening to attack me.
Second move is Assault. Try to use something that helps with your first technique. Something that gives you an extra edge. For example, I just used swamp of the underworld on you, and continue with a a wind technique that comes from the sky (there's an A-rank technique for this). You would have to get out of the swamp, and at the same time defend from the wind as it is coming down on you. Considering that you'll probably use lightning to defend against the swamp, the wind has an elemental advantage, causing it to overpower the lightning and effectively killing you.
Now third: Supplementary. The third move should be something like "clones" or a shuriken clone technique. This gives you an extra edge while the opponent is defending against your massacre from before anyways, and it will give you a bonus throughout the entire fight.
Any questions so far?