Depends on the color of the jacket and your personal style. I'd go for a baggy look with Forsquare stuff. I use mine with a Special Blend Annex pant and they snap together with ease.

Stick to a color pallet of similar colors and you'll do just great. Wood colors, earth colors or frost colors and so on. For instance I think the "Tan A Poppin" variant currently available would be awesome with a dark mustard yellow pant due to the yellow stripes. If you want to go safe buy white or black pants, they work with everything.

For more inspiration you could check out colorlovers.com, they inspire me a lot: http://www.colourlovers.com/palettes/top