Well, obviously the Tour de France  is :-) but your journey needn't be. Using a lower gear and going that bit slower can easily mean that you arrive having done some exercise but not needing a shower and change of clothes - phew!
How fast you pedal matters. Called cadence , for normal cycling you should aim for 60 to 80 rpm.
If you pedal slowly and heavily, rocking from side to side, it isn't just inefficient, it can damage your knees, hips, etc.
It's best to pedal quite fast against a moderate resistance - known as "twiddling".
For short hills it's OK to get up out of the saddle and "honk", but few of us are as fit as we'd like to be, so if you've run out of low gears then it's time to get off and walk up the rest of the way. Or ask the council to install a bike lift  :-)
As with any activity, wearing the right clothing helps. Everyday clothes are fine for shorter rides, but if you're going out for longer then it helps to dress sensibly.
Close-fitting clothes help to minimise wind resistance, but that only matters if you want to cycle fast. However, don't go to the opposite extreme - loose clothing can get caught in your wheels, pedals, etc, to nasty effect :-(
In colder weather, when you set out you'll need more clothes on than once you've been cycling for a while. So wearing a number of thin layers is good, and remember: layer down before you get hot, and layer up before you get cold.
And on chilly days, it's a sure and healthy sign of a cyclist to arrive on time and with a cold, wet nose :-)