When TeXmaker compiles a document correctly it displays the meassage
Process exited normally otherwise it either does not compile or it displays the message
Process excited with error(s). Each error will start with an exclamation mark followed by a description of the error and then the line number. Beware the line numbers are not always as accurate as you
would like. Most descriptions are self explanatory but any cryptic errors can be Googled to find multiple people trying to solve the same problem as you. The LaTeX community is very large and there are a plethora
of websites that allow users to post their problem and ask for help.
If you have multiple errors, solve them one at a time and re-compile to see if the first error has been solved. If you really cannot find the source of the error, comment out sections of the code and re-compile until the document compiles correctly. This will help you narrow down exactly which line the error appears on. The key to preventing errors from building up is to compile the document regularly.
If you type a command in normal text that should have been put in math mode then you will see the warning
! Missing $ inserted. This should prompt you to check that any mathematics in the text
has dollar signs on either side of it. The most common fault is one dollar sign typed but not the matching one.
Other typos in LaTeX commands can lead to this error
! Undefined control sequence. Check that your commands that begin with a \ are spelt correctly.
Finally, if you see the error
! Too many }'s then LaTeX has found an unequal number of curly braces. You may have typed an extra brace somewhere but equally you may have missed the matching