1/ Don't say too much, and of course, especially not the solution!
To say "click here" or "click there" is already a spoiler.
Nothing beats the feeling of having found the answer (almost) by oneself.

2/ If someone has already provided a good hint, no need to add another one
If you posted at the same time, no problem. You can even delete your post if you think the other answer is great.
Otherwise, wait to see if the player in distress is still stuck and asks again for help. Then, and only then, is it time to add a little hint.

3/ Never, never get mad at someone who is swimming in circles!
There’s nothing wrong about being a beginner, we all were at some time. And even veteran gamers know those moments when you seem to be blind.
A player can be mad at himself, but not at others.

4/ If you mention someone, use his alias
The world of adventure games is a small one, and lots of us know each other personally.
But on a forum, we strictly use the member aliases, not the real names.