Units

Two metres per second can be written as:

2 m/s

2 m·s^-1

The most important thing is: choose one type and stick to it throughout your text.

There is always a space between the number and the units, except for percentage.

5%

Here is a list for how to write units according to international standards.

Further information can be found on the Wikipedia entry on this topic. 

Choose whether you will write "1 to 2 m·s^-1" or "1–2 m·s^-1", and stick to it throughout your text.

Bonus point: so that your units don't run onto the next line, e.g. 

the liquid was heated to 37

°C and held for one hour.

you can use something called a "non-breaking space" or "hard space". This means that even if you make changes to the text, this space will never break onto a second line and the number and units will always remain together on the same line.

On Word in Windows you can get this using ctrl-shift-space and in Mac you can get this using alt(option)-space. Click here for German keyboard instructions.

Another bonus point:

The symbol connecting numbers in a range like 1–2 m·s^-1 is called an "en dash". This symbol cannot be found on your keyboard and is not the same as a hyphen in a word (like co-operation). More information can be found here.