For Single Page
Press ⌘ + to increase text size on the page.
Swipe in or double-tap with two fingers to zoom into a page (iOS-like).
Note that text zooming and page zooming are not quite compatible and may cause odd effects when combined so you should stick with either.
For All Pages
To make Safari “remember” your text zoom setting, use a custom stylesheet:
1) Create a file named defaultzoom.css (or any name you like, just make sure it has a css extension.)
2) Copy and paste in the following:
change 130 to whatever number suits you.
>100 means zoom in,
<100 means zoom out. Don't forget the % percent sign!
3) In safari, go to
Preferences > Advanced. Under style sheet, select Other... and point to the file you created.
4) You may need to restart safari for the change to take effect.
For Certain Websites
Personally, I prefer keeping text zoom level per site with ZoomBySite extension by Ceri Morgan.
It overrides the keyboard shortcuts and remembers the last text zoom level for domain.