An easy way to cut down the length of a speech is to omit any talking about yourself.
Common mistakes include:
Talking about how undeserving you are to speak at such a venue (which is either faux humility, AKA the worst arrogance, patently obvious, or both)
Talking about how little you prepared for the speech (even if due to lack of notice – the message is, “You in the audience don’t deserve the respect of a speech that sounds well prepared, or even the dignity to pretend that you do”)
Talking (in an “Out-Of-Town” setting) about how surprising it is to find B’nei Torah (or the like) “even here in _________ ” (You just slapped the entire community across the face)
Talking about how short the speech will be (you just ruined it)
Another common mistake is the belief that every speech must begin with a joke. This is totally false. It is not necessary to start with a joke. Nobody needs to hear the same corny lines again – and, yes, we heard that one already. DO NOT tell jokes unless they are truly funny. They lengthen both the actual and perceived duration of your speech, with no positive contribution.
In general, a speech should be planned. Determine the purpose of the speech (that is, what the audience wants to hear, not what you want to say) and how long it is expected to be, and develop a focused address that does not digress from its purpose or overstay its welcome.