You'd probably heard that, but I'll say it again: One of the most important conditions for success in social is consistency.
Consistency is the key to everything. No matter how good your content is, it takes time for people to see it and acknowledge your accomplishments.
Consider this example- let's say, you have to hammer a nail. You have a hammer in one hand, a nail in the other. So what would you do?
No one (if not a complete idiot) would think of doing the whole job with a single strike. Why? Most likely, you'll miss - with all sorts of consequences ranging from a dent on the wall to smashed fingers. Even if you'll get lucky and land a perfect blow, it still wouldn't be sufficient to drive the nail deep enough through any solid material.
So, again, what do you do?
You gently hold the nail and start hitting it with a series of carefully placed "soft" strikes. After that, when you're sure it won't go anywhere, you take your fingers out of harm's way and hammer it harder to drive it to the desired depth.
After all, it takes several steps with a series of well orchestrated movements to complete such an easy task. What makes you think that building your company's presence in social would be any easier than hammering a nail?
How can I nail it?
You need to develop a routine of posting every day. Not "every other day" or occasionally when you'll have some time for it. Every day. In fact, several times a day.
Some companies tweet every hour (thanks to apps such as HootSuite). You won't need that. But you have to do it at least 3 times a day. Many experts agree that 5 to 6 posts would be the optimal number. It will keep you on peoples radar but won't annoy them (it's quite irritating to see the same avatar or logo all over your Twitter or Linkedin wall).
It's considered that the best time to post is from morning till lunch or (as with Linkedin) also at the end of the workday. The best days are Tuesday - Thursday. You can find more info on this here http://ow.ly/kCSn0
However, my advise would be- don't follow it blindly. Experiment. Make an effort to post at different times and see what happens.
Again, the most important thing is that you do it regularly and consistently. Otherwise, you'd never be able to nail that beautiful picture of yours on the wall.