How to get meat on your arms

You don't sound like you have the kind of attitude that is conducive to gaining mass, but if there's one tip you should follow (assuming you want to gain mass instead of just tone), it is that you should work whichever muscle you are training to failure. That means you keep on going until you literally cannot lift the dumbell (or whatever it is) again. It'll hurt, but your body will regenerate the damaged muscle and then some extra in an attempt to avoid damage again, giving you bigger muscles. This takes a lot less time with a heavier weight.

Also make sure to keep your muscle under constant tension (i.e don't rest it somewhere for a few seconds before going for another repetition) and perform a full motion across the entire range of movement if possible. If you're skinny, 5kg is fine but you'll probably find that once your muscles have recovered, that you'll be able to lift more quite soon.

Jam it back in, in the dark.

I should've mentioned that yes, you do need to rest after exerting yourself so much, until you can feel no soreness at all. I don't actually think "kicking them when they're down" by doing lighter exercises on already sore muscles is necessarily a good idea, but as long as you know you're not just impeding their recovery I guess it's OK. I guess my point about training to failure was simply that if you only work within the limits of your body, your body won't have the stimulus to change. It would also help to regularly change the types of exercises you do, as someone mentioned, to avoid the risk of your body getting used to a pattern.

I don't care much for the more technical aspects of growth, but it can be observed by anyone that a person's physique will change to adapt to their environment. If your daily routine involves doing a lot of heavy work, you'll grow stronger (and a bit bigger) to cope. Good old-fashioned hard labour would be a perfect workout, yard work maybe.

I would prefer personally to be strong rather than huge, and to be strong you need core strength in vital groups, you can't strengthen just one particular set of muscles and expect to be strong; all that will happen is that the weaker of your muscles will fail when stressed by the stronger ones and let you down. So I agree with what Killy said earlier. Grip strength is a classic example of this; you could probably do a lot more pull-ups using those huge biceps if you could only hold on to the bar a bit longer.

There's nowhere I can't reach.