Hi everyone,
I am new to these AD&D games so when I saw them on GOG, I thought I'd give them a shot and get a feel for the classics. I have played some RPGs before, (Diablo is about the oldest CRPG I've ever played) but nothing from the 80's. I purchased the first two bundles, (the "Eye of the Beholder" series and the Gold Box series), and thought that I'd start with Pool of Radiance. The interface is very tedious and for a new player, they have a bit of a learning curve, and I've figured out how to create my party, equip, and navigate. It took me some time to figure out that I had to use the "1" key to select options instead of just using the up and down arrow keys, (for what reason is anyone's guess). What I can't seem to figure out is how to have my magic users cast spells during combat, (and yes I did memorize them first). Does anyone have any advice? Thank you all for taking the time to read this.

Remember to 'Rest' after memorizing spells. It takes your casters time to pray or memorize them. If you want a better interface, Unlimited Adventures has a fanmade conversion of Pools of Radiance and many other gold box classics.

Edit: You can also press Control-F1 to open up a keymapping function in dosbox. This may help you with the Eob games, they don't come with wasd movement controls. Just remember to swap the controls completely, not just add them to one set of keys. Setting Q to 7 needs 7 set to Q, then the original Q=Q/7=7 get deleted, not just ignored. That would allow you to rotate left. Same for the other keys. You can get a default keymap back by deleting the Mapper file in the game directory.
Hope you have fun with my favorites, the Eye of the Beholder games!

To answer your immediate question, you must memorize spells, and then immediately rest. You'll see a bunch of messages pop up saying which spells you have actually memorized, assuming you aren't interrupted by anything. The good news is, as you progress through the game, more and more areas become perfectly safe to rest in.

Getting started is really difficult. All the early CRPGs seem to have a brutal level 1 hump and Pool of Radiance is no exception. Honestly I find no shame in modifying my starting characters to have a max HP roll. It sucks having characters that always go down in one hit. After that you come to equipment, where you are given no in game feedback in the shop about what items which characters can actually equip. But the manual tells you, so just go by that. Don't get overwhelmed by the plethora of weapons that are mostly identical and just stick with a standard Long Sword for fighters and thieves, Staff for your Magic User and a Flail for your Cleric. And if I recall correctly, Thieves are limited to Leather, Magic Users nothing, and everyone else can sport up to full Plate.

There is no shame in running away from fights, and sometimes you can actually talk your way out of them as well. So always give the Parlay option a chance, and experiment with different approaches on different monsters. I think your strength or charisma, along with your level, may factor into your chances of success here as well? The attribute used is whoever your active character is, which is selected using the Home/7 and End/1 keys on the numpad.

You'll find a lot of experience comes from completing quest and finding hidden treasure. So at level 1, it could be in your best interest to avoid combat as much as possible and slink around looking for magic items. The slums actually have a ton of treasure, I think more than any other single area. It's a really great starting area. There is a false wall too, although I won't tell you where, which has a great little starter kit for adventurers behind it. You can just walk around with search active, which inspects every square you enter for treasure and traps. Or you can use the look command to only inspect the square you are in. Walking around with search active eats up a ton of time, 10 minutes per step, and drastically increasing your encounter rate.

A word of warning, avoid the southwest corner of the slums. There is a brutal encounter down there which is simply beyond the capabilities of a starting party. Come back later for those guys. Aside from that, everything in the slums should be doable. Just save early and often, and always keep one save in town with full health and spells memorized. After you complete the slums, you should be in good shape to tackle the next few areas.

Thank you both for the fantastic advice! I had no idea that you had to rest after memorizing a spell. Thanks again.

Standing on the corpses of certain 'dead' enemies in this battle will prevent them from standing back up. Also, using the doorway as a bottleneck makes the battle much more survivable. Have the Fighters hold the line, while everyone else heals or attacks from range.

The Sleep spell won't work here, because I think the monsters in this encounter are too powerful to be affected, but I think at least Hold Person will do the job in a pinch (I can't remember if would work on these enemies, but it is worth a shot)

Edit: I did some Googling to double-check, and maybe the Sleep spell will work in this encounter? At least on some of the enemies? I wouldn't be surprised either way; I just can't remember the relative power of these enemies in this edition (I really wish I still had my First Ed. Monster Manual about now...)

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All in all, the advice has been pretty spot on. I will note one thing though. If you max out the statistics of your party, the random encounters will be a bit tougher. As I recall, the game tries to balance out the relative power of the random encounters to keep it more of a challenge (usually just by increasing the number of opponents).

I still advise you just max out everyone's prime attributes at least (Int for mages, Str for fighters, etc), or even just give everyone perfect stats in everything, as it will make your party much more survivable in the long run, but do know that it will make the beginning of the game a slight bit more challenging.

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Lastly, the Sleep mage spell is your friend for the first few areas. It can enable your front-line fighters to kill swaths of helpless low-level enemies. As the game likes to throw dozen of low hit-dice enemies at you quite often, it can make a tough battle trivial.

That's hilarious! :D

Yes... I remember when I realized this. It changed this combat from "systematic party-wipe" to merely "challenging but winnable". It also works if you lure enemies to stand on their friend's bodies, which is even more amusing. ;)