if i blow a fuse in my house, do i replace it just just by going off what amp.it is?

always replace with an identical fuse,they make "slow blow" fuses now that don't fire as quick ,they need a longer sustained amp surge to burn out . suspect the heater is blowing the fuse during heating up and not in full use if so ..slow blow will fix you. but don't use a higher amp fuse

YES!! The fuse is sized to protect your wiring, so if the fuse blew , then something else is wrong. The circuit is overloaded ( to many items plugged in, or a short has occurred). Unplug/turn off whatever is affected, replace the fuse and if it doesn't blow right then you don't have a short.

Yes assumeing that it was the proper size to start with.

Keep in mind that your lighting circuits and Receptacles should not ever be more than a 20 amp circuit at the most some might be 15 amp. The only things that come to mind right at the moment that might need a 30 amp fuse is water-Heater & Dryer.

Yes but try and find out what blew it in the first place before you replace it.