So I will be getting my car on the road again after being outside my house gathering cobwebs for the last 3 months.

But I was just wondering what should be the "start-up procedure"?

I will need to jump it because the battery is dead.

Cheers

Charge the battery first then just start it?

As above. Before driving it make sure the tyres are all correctly inflated, be prepared for the brakes to be shit until you've worn them back in. If the handbrake was left on for 3 months it may require unsticking. If it were me I'd probably whip the cam cover off and pour a bit of fresh oil over the cam(s), but then that's just me!

crank it manually, build up oil pressure.

Unplug the hall sender and crank it until the oil light goes out. tbh though 3 months isnt a great deal of time to be that worried, battery will prob need to be replaced, but charge it 1st just to give it a chance.

I'm with the above, better safe than making work for yourself, it all depends on whether or not any moisture has got in there.

I used to leave mine for months when i was at uni, just a charge of the battery used to do for it. Would run fine after that

i got a 85 civic gt started after 11 years of being barn stored, after doing a bit of basic cleaning i just fired it up, 3 months isnt anything for the engine the only thing i would be concerned about is the valves being dry and then fired straight back up but i wouldnt bother taking of the cover. just drive it as soon as it starts rather than letting it tick over for a bit. engines that have been stood for years are usually no good as the seals go but 3 months i wouldnt worry at all.

just start it up like normal