To extend a little:

> tail -f

Or

    tail -f filename-to-watch

if looking at a file that might be renamed and stop updating (i.e. log files that are rotated). Without a filename the file descriptor is followed so when for instance access.log becomes access.log.1 your display keeps following access.log.1 not the new access.log which is probably what you want.

> find . | grep

I add “-type f” to find's params when doing that, as I'm almost invariably doing something that I don't want to apply to sub-directories (just the files within them).

Also if sending the file list to grep for searching the contents not the names:

    find . -type f -print0 | xargs -0 grep options-and-stuff-to-find

which deals with the common issue of spaces in filenames. Or you can do

    find . -type f -exec grep stuff-to-find {} \;

to avoid the extra invocation of xargs, but I consider this less beginner-friendly (you have to remember the “;” and that it usually needs to be escaped or the shell will take it as an end of statement marker and not pass it to find, the error message “missing argument to `-exec'” received when you forget it not particularly helpful IMO if you don't know _or_ temporarily draw a mental blank).