How to simply remove everything from a current or specified directory on Linux?

Several approaches:

1. rm -fr *
rm -fr dirname/*
   Does not work — it will leave hidden files — the one's that start with a dot, and files starting with a dash in current dir, and will not work with too many files

2. rm -fr -- *
rm -fr -- dirname/*
   Does not work — it will leave hidden files and will not work with too many files

3. rm -fr -- * .*
rm -fr -- dirname/* dirname/.*
   Don't try this — it will also remove a parent directory, because ".." also starts with a "."

4. rm -fr * .??*
rm -fr dirname/* dirname/.??*
   Does not work — it will leave files like ".a", ".b" etc., and will not work with too many files

5. find -mindepth 1 -maxdepth 1 -print0 | xargs -0 rm -fr
find dirname -mindepth 1 -maxdepth 1 -print0 | xargs -0 rm -fr
   As far as I know correct but not simple.

6. find -delete
find dirname -delete
   AFAIK correct for current directory, but used with specified directory will delete that directory also.

7. find -mindepth 1 -delete
find dirname -mindeph 1 -delete
   AFAIK correct, but is it the simplest way?