How can I set the position that terminal opens at?
Most terminals can be launched using the geometry switch allowing you to specify terminal's size and position (COLUMNSxROWS+X+Y) e.g.:
gnome-terminal --geometry 73x31+100+300
or
xterm -geometry 93x31+100+350
If you want to make the above permanent, copy the terminal launcher (terminal's .desktop file) from /usr/share/applications/ to ~/.local/share/applications/ and edit the Exec field accordingly.
E.g. for gnome-terminal
Exec=gnome-terminal --geometry 73x31+100+300
Having that custom launcher in your $HOME would preserve your settings after terminal-package upgrades (that would otherwise overwrite the default .desktop file in /usr/share/applications).
xterm Options Using Xresources or Xdefaults
This is the general "syntax" for options that go into the ~/.Xresources or ~/.Xdefaults file:
XTerm*geometry: COLUMNSxROWS+X+Y
For example
XTerm*geometry: 90x30+0+540
Note: The first two options (COLUMNSxROWS) depend on your font type/size.
Furthermore, it also depends on the resolution of your Display, as the last two options are for the position of the window; this is calculated in different units than the Window Size of the xterm window.
When X = 0 then the position is all the way on the left
When Y = 0 then the position is all the way at the top
If your resolution is e.g. 1920x1080, then you'd put the Y value as 540 (half-way down from the top edge of your display); as the 30 ROWS value is roughly half the display height on the same-sized display using my own system's fonts, settings.
- Xresources ArchWiki
As an update, the top answer didn't work for me in Ubuntu 18.04 as of Aug. 2018. What got the job done is Hardware -> Keyboard -> Add new command (By hitting plus sign). Fill in the "Command" field with command like gnome-terminal --geometry 80x55-500+0. Set the hotkey as Crtl + Alt + T. Done.
Even better, you can add the command to "Startup Applications" to launch the terminal at startup.