Just like in the docs:
$user = User::where('u_id', '=', $userid)
->where('type', '=', 1)
->where('is_active', '=', 1)
->select('firstname', 'lastname')
->get() / first()
// or
$user = User::where('u_id', '=', $userid)
->where('type', '=', 1)
->where('is_active', '=', 1)
->get(['firstname', 'lastname']) / first(['firstname', 'lastname'])
However If you want just some of the columns, then I wouldn't use Model, but rather simple array.
So better tell us what the purpose is.