effective way of positioning things?

What is the most effective way of positioning things? Derma panels to be exact, they always end up where I prefer they shouldn’t be…

Use multiples of the ScreenHeight and ScreenWidth
Example:
[lua]
local sw = ScrW() --Width of the screen
local sh = ScrH() --Height of the screen

panel:SetSize(300, 150)
panel:SetPos(sw * .5 - panel:GetWide() * .5, sh * .66 - panel:GetTall() * .5)
[/lua]

Another really useful function is panel:Center() - which centers it to its parent.