When researching newspapers, you will be sitting at a microfilm reader that has either an automatic fast forward and/or reverse button, or you will be turning a small handle to move the film from page to page and edition to edition, also know as issue to issue.
If you are sure of the date something was published, your task will not be too difficult. You will quickly learn to spot the front page of each edition and, by moving along in chronological order, you'll find the date you are looking for. Any paper published in the past 50 to 75 years is going to have a fairly consistent format so you should soon be able to recognize the areas of the paper, and often specific pages, where obituaries are listed. This is helpful because obituaries are normally printed in every edition. If you are looking for a wedding or anniversary record, you'll find that society items are normally printed on specific days. That is usually the Sunday edition which is also normally the largest edition for a daily newspaper.
If you are searching a paper that comes out less frequently, say weekly or a few times a week, then you will want to look at least two weeks prior and two weeks after the event. If that is not fruitful, expand your search in both directions.
If you are working from an estimated time period, your task may take longer; but, again, the format of the newspaper will be the key to opening the door to that particular event in your ancestor's past.
If you are working with more recent time events, be sure to ask if there is an index. You may spot a surname reference that you did not know about—perhaps the birth or death of a previously unknown family member.
In most cases, there will be the ability to photocopy an individual page. But, what if that copier is nonexistent, or broken down? Carry a camera or even a hand-help photocopy machine, if possible. And, take copious notes. In this electronic world, Murphy's Law comes into play too often. Backup is always necessary.
Some microfilm can be very difficult to read. You may find that a photocopy of the page is easier to decipher. I have heard that some researchers carry along a piece of clear yellow acetate. They say that placing it over the image makes it easier to read. Take a magnifying glass, or some other form of magnifier. Being prepared counts here just as it did in the Scouts.
When that item you are looking for surfaces, what you have in front of you is primary source data. Primary sources are sources that occur at or near the time of an event. Stop immediately and record the name of the newspaper, the date, the volume and edition number and the page number where you found the item.
When you can, take time to post the data you found to the appropriate surname message boards. Your fellow researchers will appreciate it.
Newspaper Research: Part 1, An Overview
Newspaper Research: Part 2, Which One and Where