Unfortunately its possible that you will during the pdflatex
command run to TeX related errors and the process stops (pdflatex will
print a lot of scary looking messages, but unless it stops you can
ignore them without much harm done). First, do not panic. You can get
out of pdflatex by typing X and Enter. This will abort the
TeX process.
When an error happens, you should understand why. First task is finding where in the document it is happening. The line numbers reported by TeX refer to the .tex intermediate file corresponding to your .pd. You may examine this file and try to understand the cause, or you may just try searching in the .pd source for the text that appears to be causing trouble.
Unless the cause is trivial, or you are a TeXpert, the chances are you are stuck. At this point, either try to get TeX help (read a book, try Google) or try trial and error to see which part of the document is causing the indigestion. You can eliminate parts of document by enclosing them in ignore clauses, or just by deleting them entirely. Often this is an iterative process of trying a fix, regenerating, and previewing. Do not give up.
Be suspicious of special characters in complex constructs getting misinterpretted.
Beware that sometimes a structure that does not close, may cause weird errors far down the line. A very common case of this is when you use the empty line hack to introduce wide table columns one per line and you get out of sync.
To cram little more on page use
< <tex: \enlargethispage*{\baselineskip}> >