Not all sentences make a single point -- compound sentences, especially, may present several equally-important pieces of information -- but most of the time, when you write a sentence, there is a single argument, statement, question, or command which you wish to get across.
When you are writing your sentences, do not bury your main point in the middle; instead, use one of the positions of emphasis at the beginning or end of the sentence.
The Loose Sentence
If you put your main point at the beginning of a long sentence, you are writing a loose sentence:
I am willing to pay slightly higher taxes for the privilege of living in Canada, considering the free health care, the cheap tuition fees, the low crime rate, the comprehensive social programs, and the wonderful winters.
The main point of this sentence is that the writer prefers to live in Canada, and the writer makes the point at the very beginning: everything which follows is simply extra information. When the readers read about the free health care, the cheap tuition fees, the low crime rate, the comprehensive social programs, and the wonderful winters, they will already know that these are reasons for living in Canada, and as a result, they will be more likely to understand the sentence on a first reading.
Loose sentences are the most natural for English speakers, who almost always talk in loose sentences: even the most sophisticated English writers tend to use loose sentences much more often than periodic sentences. While a periodic sentence can be useful for making an important point or for a special dramatic effect, it is also much more difficult to read, and often requires readers to go back and reread the sentence once they understand the main point.
Finally, it is important to remember that you have to structure a loose sentence as carefully as you would structure a periodic sentence: it is very easy to lose control of a loose sentence so that by the end the reader has forgotten what your main point was.
The Periodic Sentence
If your main point is at the end of a long sentence, you are writing a periodic sentence:
Considering the free health care, the cheap tuition fees, the low crime rate, the comprehensive social programs, and the wonderful winters, I am willing to pay slightly higher taxes for the privilege of living in Canada.
The main point of this sentence is that the writer prefers to live in Canada. At the beginning of this sentence, the reader does not know what point the writer is going to make: what about the free health care, cheap tuition fees, low crime rate, comprehensive social programs, and wonderful winters? The reader has to read all of this information without knowing what the conclusion will be.
The periodic sentence has become much rarer in formal English writing over the past hundred years, and it has never been common in informal spoken English (outside of bad political speeches). Still, it is a powerful rhetorical tool. An occasional periodic sentence is not only dramatic but persuasive: even if the readers do not agree with your conclusion, they will read your evidence first with open minds. If you use a loose sentence with hostile readers, the readers will probably close their minds before considering any of your evidence.
Finally, it is important to remember that periodic sentences are like exclamatory sentences: used once or twice in a piece of writing, they can be very effective; used any more than that, they can make you sound dull and pompous.