Carrying an ugly heavy monkey on your back on a long hike is NO fun, which is why I recommend a technical or “hiking” pack for day hiking, weekend hiking or longer. Hopefully you agree with me, that a backpack does more than just hold your gear or necessities.
If your a brand junkie, look at Osprey, Arc’teryx, Kelty or Gregory for starters.
Your choice of backpack is pretty important, since you have to lug it around with all your stuff in it – you really need it to be supportive, comfortable. Especially if you’re planning to do more travel in the future – the quality/structure of the bag is as important as the size.
I would go to a camping store/travel shop and try on all the bags, decide which you like and THEN see if you can get it cheaper online or at a sale.
Regarding size, it comes down to personal preference. Many people can and do travel with a 30-40 liter bag (and you don’t need a bigger bag for a longer trip – take the same stuff and wash it) but others prefer a bigger bag so they can bring back souvenirs.
I have a 50L pack but it can be compressed down really small using the straps – so I usually only have it a third-half of the way full when I leave home. But sometimes I buy stuff on the road, or pick up books to read etc, and it’s nice to have the option of using some of that extra space.
I travel with a small daypack too – usually 10L if it’s backpack style or less if it’s purse/satchel style. It’s helpful to have something to carry water, a guidebook and camera around in while out sightseeing.
And so, to help you find the right backpack for hiking, I’ve listed some good quality packs that are designed for extensive day use in the back country or just heading out your front door for a mountain hike.