Reputable newspapers have the following characteristics:
Cover serious topics, such as politics, economics, environment, education, etc.
Have professional editors and journalists on staff
Been published for a number of years
Have professional-level design, grammar, and word usage
Contain a preponderance of text over images
Articles contain evidence or data to support claims
Are indexed/abstracted in databases used in academics
Also remember these points about newspapers:
Online newspapers can be just as reputable and reliable as print newspapers
Newspapers contain different types of articles - research, editorial, opinion, column, report. Be sure to determine whether the article your are reading is stating fact or opinion
Tools for Evaluating Newspapers
The word "periodicals" includes both journals and newspapers. Here are some tools to help you determine the bias of periodicals, what type of review they have (peer or editor), how long they've been published, and more.