Change command module

I've found two potential solutions to this:

Minimize the Nav Ball - this prevents shift from activating the thrusters

Double-click to focus - If you can see an object, you can double click to focus on it.

Don't go onto an EVA when you are still flying through the atmosphere or your kerbal will get blown away.

When you go on EVA, always press F as fast as possible to grab the ladder at the hatch. Sometimes the kerbal will already be on the ladder when you go on EVA and get right back in, but when he isn't, the chance is high that he will drift away when you don't grab the ladder quickly. When the kerbal goes drifting, you can activate his jetpack with the R key and attempt to maneuver him back to the hatch, but this takes a bit of practise.

By the way: You can also obtain science from the surface of Kerbin. It doesn't give you many science points, but every terrain type gives you other results which add up. It's enough to unlock the first few tech nodes. Low-hanging fruits to pick up early are crew reports, eva reports and surface samples from:

• Launch pad
• Spaceplane Runway
• Space Center (everything around the buildings which is not one of the two above)
• Shores (the flat plain around the space center)
• Grasslands (the slightly hilly area to the west)
• Highlands (the more hilly area further to the west)
• Ocean (your Kerbals can swim)

The first two can be easily picked up without even igniting your engine. The others only take a small sub-orbital flight (or a bit of walking)