Structure of participation in a Group Discussion:

If you plan on being the first speaker then remember it is a high risk, high return strategy. If you can make a good opening statement, which is relevant and sets the tone for the Group Discussion, it will be in your favor. If you do this well, you may automatically become the group leader. However if you bungle it up (by speaking for the sake of speaking, not really having anything pertinent to say), it will be remembered and will be held against you. So take care of your words, use them only when you know you can make an impact.

Being the first speaker is a high risk, high return strategy

In case you could not be the first speaker, do not be perturbed. In any Group Discussion, there are crests and troughs during the discussion. The Crest is when the noise level is at its peak.  The trough is when there is almost total silence. Ideally, you should enter the Group Discussion during the trough period. But in competitive Group Discussions, the crests occur more often and troughs may not occur at all. In such cases, you could identify the stages in the Group Discussion, where ideas dear to you are being discussed and enter the Group Discussion irrespective of the noise level.
When the noise level is too high then identify the most powerful speaker in the group, and note down the points that he/she is making mentally. The moment the noise level reduces a little, enter adding on to what the powerful speaker spoke. You will have, most likely, made a strong ally who will carry you through the noise.

Try to speak as many times as you can. Just make sure that it is relevant to the topic and that there is a connection between what others are saying and your views. Do not be bothered about any possible bias that the moderator might have, as that is a factor beyond your control.

Remember that a Group Discussion, is a discussion, not a debate, and hence it is no recommended that you take any stand in the Group Discussion. Not taking a stand indicates you are a mature, flexible and objective person. By taking a stand you are limiting the scope of your discussion. Because then you have to stay within the ambit of that stand, and can’t look at other angles of the issue without appearing to contradict yourself. Do not get into this trap. You may participate actively by pointing out all the angles of the issue in a reasonable and logical manner, without taking a stand on any one point of view.  In a Group Discussion some other participant’s counter-argument may convince you. If this happens, then it is best if you accept it without doing a complete volte-face by explaining to the group how your previous argument was true within a narrow range, and how the new one is applicable to a broader range. Be aware that if you do not do this convincingly enough, the panel may view you as being weak-willed and externally controlled. So that wisest strategy is to think before you speak so that you do not end up putting your foot in your mouth. However, if you have a radical line of thought on a topic, as long as it relevant, you are free to be vocal on it. In fact it would demonstrate you creativity.