This is a bench design that I developed building park benches from discarded scraps at construction sites.
Step 1: Gather Materials
Here are some rough estimates if you're going to purchase wood to build a bench.
5 Planks - I usually shoot for five (5) 2x4's cut to somewhere around 4 feet each
2 Front Legs - two (2) 2x4's cut to about 15.5 inches each
2 Back Legs - two (2) 2x4's cut to about 32.5 inches each
2 Supports - two (2) 2x4's cut to about 19 inches
2 back supports - two (2) 2x4 scraps cut to 5 inches each
Screws - it's nice to have a bunch of 2.5 inch screws and some really long deck screws to hold up the back legs
You could use nails.
Paint - I always buy mistint paint. Most paint stores keep paint that they've botched for another client and they try to sell it for cheap. Look for some ultra high gloss outdoor stuff. I try to avoid the solvents and the oil based - personal preferences.
A level - unless you really trust your eyes
A saw - you could do it by hand if you really needed too (also you may try to charm a Home Depot employee to make your cuts)
A drill - with a screw bit for all of these screws or a hammer if you opted for nails
A tape measure - unless you REALLY trust those eyes of yours
All of the benches I built were different, since I was using found materials I needed to change the plan around depending on what I could get my hands on. Obviously those back legs could be lower and you could use the planks from pallets to get yourself a loveseat design that might be a bit lighter. If you follow the above measurements you can build this small loveseat bench using four (4) 8ft 2x4's. With the screws and paint, you should be able to do this for less than $30. If you use recycled lumber it will be even cheaper, and maybe even more interesting!