How vs. What
Today I want to address a mistake that is very common among non-native speakers, namely the confusion of how and what … like in forming questions. While I always had a reasonably good intuition when to use which, I learned that there is actually some logic behind it.
According to my trusted book Practical English Usage, how is used to ask about things that typically change (weather, mood, health), whereas what … like is used to enquire about things that usually do not change (looks, character). For example, you would ask
How is John?
if you are interested in his current mood (fine, stressed out, …), whereas
What is John like?
aims at understanding what kind of person he is (charming, funny, …).
How does Jane look today?
refers to her appearance as determined by clothing, make up, etc. In contrast, the answer to
What does Jane look like?
will include her hair colour (which may change, but usually does not daily), her built, etc.
When it comes to asking people about their reactions to certain experiences, either how or what … like is acceptable. For example, you can use either
How is your new job?
What is your new job like?
Finally, English allows either how or what … like, but the combination how … like is not grammatical. Especially German native speakers often ask incorrectly
How does the function look like? (Wrong!)
What does the function look like?
A simple mnemonic that works well for me is that ‘Like what?’ sounds OK, whereas ‘Like how?’ does not. A simple way out is to change the question to just
How does the function look?