Multitasking helps in managing multiple things in one go but that is not always a good idea as it hampers the productivity to a greater level. In order to have better productivity at work, you must learn few habits and have a work life balance.
Choose one task and manage that before even thinking about another one. As soon as you get over with that, move to the next one. This would help your brain think more and work better.
While you are in the middle of discussions with a client and suddenly new ideas start popping in your mind. You still need to stick to the discussion that you are in with your existing client. Finish your meeting and now start focusing on the new ideas.
You will get distracted only if you wish to. You can always lock yourself away from the distractions around.
Either meditate or spend some time alone. This is equivalent to any mind exercise that helps in increasing your attention span.
Always saying “Yes” to your colleagues will get you under pressure to handle many things at a time. You must learn to say “No” as at some situations, saying “No” saves you from lot of hassles.