Not sure if you mean opening a new empty tab, or opening a link in a new tab.
To open links in a new tab by default, tools->options->tabs, select the option to open links in a new tab. Or middle click if your mouse supports it (even the cheapest ones do so there's no excuse really).
To open a new empty tab, double click the empty space next to the last tab.
I prefer ctrl+t to open new empty tabs anyway because the first thing that you usually do after opening a new tab is to type in a URL, and straying from the keyboard to the mouse/touchpad consumes more time