i recently wrote about using ping to pause for a number of seconds in a batch script. It was brought to my attention that you can use /wait to actually wait for a process to complete like so:
start /wait /i "unimportant title put whatever here" "C:\path\to\some\executable.exe"
or if you have an msi installer you can do this:
msiexec /i "C:\path\to\msiinstaller.msi" /qr