No, I don’t mean that your presentations are pointless by definition. It is juist that too many speakers think that they should keep their conclusions a secret until they get to the end of the presentation. They feel that arguments should come before conclusions and that it would be impolite to “spill the beans” before the pros and cons of all possible solutions to a problem have been thoroughly discussed.
However, we’re not talking about philosophical or ethical issues where a buildup like that might be required, we’re talking about presentations that deal with technical solutions to problems. Your audience will want to know what your expert opinion is, and why. In that order. And don’t beat about the bush; some people will have to leave the room before the end of your talk, and they should still know what your conclusions are before then.
So instead of saying something like “today I am going to talk about the three concepts for our power source”, which keeps your audience guessing which one you think is best, you should give them the bottom line first. Say “I am here to explain why we should use lithium ion batteries to drive our device”, right after you have introduced yourself. This way, your audience will know what to expect from the rest of your talk.
Maybe you have heard of the “Tell Them Technique”, which builds on the same idea: in the introduction you Tell them what you are going to tell them, in the body of the presentation you Tell them, and in the conclusions you Tell them what you have just told them. This way you give them the bottom line three times. By then it should really be clear what you’re trying to say to them.