Hi, Glad to see your researching first before buying, best thing to do is have a nosy round in the site and check out different threads etc..you'll gain lots of info from that.
Like someone else said, have you considered getting 2, they are very sociable animals, and id al;ways recommend you get 2, as they will keep each other company, if your getting males its best top get 2 which are already together as babies as you wont have a problem with them fighting hopefully, although be aware that males do scent everything i have two boys and as soon as the cage has been cleaned they go in and scent everything up! girls on the other hand dont lol i had females as my first piggies and personally id say go for girls, they dont fight the same as boys do, and from my experience tend to be more on the cuddly side. ive got 5 girls and 2 boys, and my boys fidget like mad even though they get handled everyday, where as my girls will sit and cuddle more.
always check that the guinea pig is healthy when buying, it should have no mucus around the mouth or nose, there should be no patches of baldness/itchy/flaky skin, the eyes should have no crustyness and should be bright and overall the guinea pig shouls look well, if you buying from a store watch the piggie for a while to make sure it running around, eating//drinking ok.
the cage should be large enough for the piggiy to run about and popcorn easily, if you have 2 you'll need to adjust the cage size accordingly, if space is a problem you can always make a double layer cage with a ramp..giving more room, My boys live in a cage inside, and my girls have half the shed converted into a big run for them as a cage, and in summer i build a big outdoor run on the garden for them to play out in duiring the day, put them back in cages at night..always remeber to either put a net/roof on any run outside to stop cats etc getting to them, i normally sit out with mine to keep an eye or the dog lies down and watches for anything coming into the garden.
there are many types of bedding, if they are being kept indoors i would strongly recommend the towels and polyester method, its much more cost effective too, you layer 100% cotton towels down, and cover with a 100% Polyester sheet the towels soak down the pee, leaving no smell, and your guinea stays dry and you can sweep off the poop daily, it keeps them really clean.all you have to do is scoop the lot out and put on a wash once a week O0
They need fresh vegetables/fruit, hay, dried food/pellets, and water daily. the veggies can be quite costly but if your only having 1-2 guinea pigs it shouldnt go too bad, some of the fav's are cabbage, brocolli (flower and stalk), carrots, celery, cucumber, apple (not too often), tomaotes, babycorn, peas in pods/mangetout, parsnip, courgette, cauliflower leaves, bananna, strawberries, orange, grapes, kale, and lots more! there is a shopping list which you can print out and keep for reference
when picking a dried food, id go for pellets and it stops selective feeding, with the mixes they tend to pick the bits they like, and leave what they dont meaning they arent getting everything from their food mix - meaning your wasting your money because you can probably bet they are eating the things which are of the least nutrition but the best taste! there is a list of foods in the food section as you go in, people have commented on which they think it best.
hopefully that has helped you, if you need anymore info..feel free to ask or pm me
They do really need some time of run/pen for inside the house though so they can have floor time. (or you can piggy proof a room and let them run around) They need a constant supply of hay and water. They need vegetables daily (have a read through the food forum) because they cannot make their own vitamin C . They also need their dry food (mix or pellets). 