I am fan of your mails these days since I registered. I would like to inform you that I received an email from a consulting firm showing interest in my application.
I am now asked for my salary expectations. I have been surveying online but would like to seek your opinion regarding this.
Based on this information, could you please provide me some helpful information?
The safest answer is to say your salary expectations are to receive compensation competitive in the industry for someone with your background... which is a friendly way of saying, "I don't plan to give you a number."
When I interview people, I always ask this question for the reasons I stated above -- to weed out people who won't be happy at the compensation level I had in mind and to see who I can get a good financial deal with, assuming I like their skills.
If you say a number and it is too high, they may pre-judge you as not taking an offer they might otherwise extend. So a number that is too high risks not getting any offer.
If you say a number and it is very low, they will decide independently whether or not to give you an offer, and if they do decide to give you an offer, it will be at the number you stated (even though they were willing to pay you a lot more).
So if you aim too low, you risk getting underpaid.
So the safest choice is to not provide any specific number. Use words like, "looking to be competitive," "I don't know the industry that well, since you know it better than I do, I trust you will make a competitive offer if/when it is appropriate to do so."
Basically, decline to answer in a really polite, reasonable sounding way.