Best thing to do is google "Camshafts explained" and "How to pick a camshaft" and do a lot of reading. There's a bunch of good articles and YouTube videos that explain how a camshaft works and how to pick one to suit your needs.
You will need to know the rough weight of your truck, decide what your intended usage for the truck is, your rear gear ratio and engine size. Also whether the truck is a stick or an auto (can go with a bigger cam in a stick truck without extra parts, a big cam in an Auto truck needs a higher stall torque converter).
For example, when I first built my truck I decided on my rear gear first. I already knew I was LS swapping and would be putting in a 4L60 auto. I've had previous trucks and cars with 3.73 and 4.10 gear ratios and liked where that put me at cruise on the hwy so I picked 3.90. Then I evaluated the engine (5.3) and what I'd be using it for most (roadtripping and daily'ing). I knew I wanted a lumpy cam but also knew I didn't want a huge converter. So I chose Circle D's basic streetable 3000 converter. So then that gave me a rough cam range to shop in, I knew I'd be ~.550-.600 lift but no more and nothing more than high 220s duration. Ended up with the BTR Stage IV V2 truck cam (.553/.553 lift 224/230 duration 109 LSA) and it was a great combo. It was still just a smidge too much cam for the converter, it would try to walk through the converter at stop lights but it wasn't bad. Drove the truck all over the country like that and loved it.
Then I decided to put a T56 6-speed in it. I also was fighting an oil leak so I decided to pull the motor to fix that and you know how it goes "while I'm here", I decided to put a bigger cam in it since I didn't have to worry about a torque converter anymore. So I went with the Texas Speed Bald Eagle N/A cam (.600/.600 lift 227/234 duration 111 LSA). I did lose some low end grunt between the more aggressive cam and the taller first gear in the trans but that was ok because I wanted the sound and more top end because I intend to autocross and track the truck eventually. Because of the increased lift, I also upgraded to double valve springs with higher seat pressure and upgraded my rockers with trunnion bushings for longevity and smoother operation.
I tell you all that as an example. You can just slap a cam in the truck and be on your way if you go with a mild one, but there are alot of other things that are affected. And that list grows as you get more aggressive with the cam. Just keep that in mind.