Good idea, but where should this advice be best placed so that new members particularly will see it before they post?
Some very long-standing members are literally 'blue in the face' having to frequently request that members asking for advice/info give us something to work with, i.e. help us to try to help you.
Another few ideas -
This is a very polite, friendly site, so it would be nice if, instead of just asking their question, a new member 1st posts in 'Newbie Central' introducing themselves and perhaps giving a little information on their model of car and if they wish, a little about their background in car repairs e.g. new to this work, some experience as a DIY'er, previously restored a car, ex-motor Mechanic etc. - this will enable any responders to word their response in an appropriate manner.
Don't forget to thank a responder for their attempt to help you - none of us here are being paid for our time or the giving of hard to find information.
You don't even have to write 'Thanks', just click on the 'like' button at the bottom of your reply.
Before responding to a question, look at the location (if shown) of the member and consider if your response in pertinent to their location - if the poster is in e.g. the U.S. or India, it might not be much help to give contact details of a local store/supplier in the U.K. as they would likely prefer a nearer supplier.
If you come across a thread when searching that you decide to answer, check the date of the thread, some threads might be several years old and the op never returned after his question was answered. So probably pointless to reply.
Also, if it's an old thread or even if it's a current thread, it would show respect for other members efforts to read all the responses to date after the thread was posted to see if the info you're about to give has already been posted by another member, instead of breezing in 'late to the party' and repeating something already said as if it was your idea.