How do I make sure my engineer spends more time working and less time reading Twitter / Hacker News?

I had this situation and I found out the hard way that it's better to cut him loose now than try and "manage him". I found that a motivated B developer is heads above an A+ prodigy who goes off on tangents. Give him an honest assessment and send him on his way.

Michael is correct, the problem lies with you, not your engineer. You said he barely gets anything done. If that's true, is he missing deadlines? Is he failing to meet any of his deliverables? One of the reasons he's getting bored is because he's not being challenged enough. He's also not motivated to try harder. Have you tried giving him (or her) difficult assignments with aggressive timelines? If deadlines are being missed, how often do you track progress? Perhaps you need to be more aggressive and track progress more often. There are many people who have ADD or ADD type characteristics. Try to control the situation by developing a daily routine where he has something new to do before boredom sets in. Even ten minute coffee, laugh or strategy breaks at certain moments is enough to get him back on track. If you can't keep the engineer motivated then perhaps you need someone who can do a better job. Leading workers is much different than managing them. As a leader, you inspire followers and keep them motivated, otherwise, you're just managing workers who are simply looking to collect a paycheck.

Make sure your engineers have challenging goals. If your engineer has enough time to spend on twitter and other sites but he still delivers code on schedule and with quality than it doesn't matter what he does in between tasks. Engineers usually have bursts of concentration and they need some time to relax the brain in between tasks. An engineer will not have 100% concentration from the minute he steps into the office to the minute he leaves.

1. Set goals and objectives; 2. Tie compensation to those goals and objectives. 3. Provide for regular feedback loops. 4. Make sure he has a job description and has signed off on it; and 5. Have a computer/internet use policy and a social media policy and enforce them. 6.  Agreeing with Eric, otherwise, cut him loose.

Cut him loose. Better yet, first sit him down, explain your situation and get him to see that results are the #1 priority, not abilities. Then set practical goals and deadlines (make sure he agrees with them). If he still misses them, then cut him loose. This isn't elementary school, and you don't have time to coddle, cajole and handhold.

If you are a startup, then suggest to him he is already living the life. Otherwise, ask him if he has a genuine difficulty gathering his focus, and ask him to suggest what might be possible to work around the difficulty. As other posters said, pair programming, making commitments etc can be pretty effective.

I usually find myself most effective after my boss or manager has reminded me that I am in fact *his* engineer and must have exactly the work habits he expects of me.

If he already knows how to do everything and build everything, he should obviously be transitioned to management.

Sometimes this is not an issue that can be solved by management tactics: A good friend of mine after few years of having those troubles at work decided to visit the psychiatrist; sometime later he was diagnosed with Attention Deficit Disorder. After few years of taking medications he was able to perform as expected.