I've been trying in vain to figure out how to use rations in this game. I tried every button on my keyboard, but none of them did the trick. I then was told by someone that rations automatically activate when your health bar hits rock bottom. Well, that didn't work either. So, can any of you guys help me out? Thanks.

press F3 for inventory, select the ration and just press 'space' or your firebutton to use it. If I remember correctly, with Metal Gear 2 - Solid Snake, having the ration selected when you run out of energy it is automatically used, but Metal Gear 1 doesn't.
BTW have much fun playing this game and be astounded with its quality

Thanks for the help. It should be a tad easier to progress through this now. It's tough, but it's pretty cool.

For MG1 If you are in a room and you take the ratio,then it would be very tiring to go through the exit and reenter to get another one.Instead press f1 for pause f4 or f5 for save and cancel saving.Then resume the game with f1.You will see that new rations are there (the same trick works with ammunition,or missiles etc).

nikodr: I actually found shifting rooms a lot easier than having to misuse my keyboard all the time. However, the trick you mentioned actually DOES work well when crossing electric floors - you won't get electrocuted when you follow nikodr's orders, smrpg99! You will find this trick will come in handy at ~some point~ in the game

You can pull off something similar in Ys II (IIRC, but it might as well be Ys I).
There's a chamber near some old geezer in which you keep losing HP.
Save, then load again and the chamber will be safe.