What can I do to boost my WIFI range?

Move the router. Higher up is generally good, but experiment. You might try rotating it or its antennae too.

If your router takes changeable antennae, get a higher-gain antenna. Bear in mind you don't get something for nothing, gain works by focussing the signal which means in other directions it becomes weaker. "Omnidirectional" antennae have weak spots upwards and downwards.

If you're using a USB wireless adapter try a different one. The "mini" ones that are hardly bigger than the USB port have poor range.

If you have a large area to cover, try a wireless repeater.

You can just DIY a booster with a beer can. Generally it will update WiFi bar to 4-5,http://www.mywifirouter.me/blog/making-a-wifi-boos...

Thanks for both answers. Beer can helped a bit.