If you are working with a good REALTOR in the area they should be able to help you with a offer strategy.
The Agent working for you, the Buyers Agent should call the Listing Agent to inquire if they have any pending offers before you submit your offer. Once you find this information, you can decide how much you would like to offer.
If there are no other offers on the property, then it may be a good idea to offer lesser amount than asking. The Seller can always counter offer if they feel you offer was too low.
If the home has been on the market only a few days and there are pending offers, then its typically best to offer your best price up front.
I cant stress enough how critical it is for a Buyer to have their own Buyers Agent working for them. If you are a Buyer and are talking to the Listing Agent to make an offer, then your interests are not being protected. The Listing Agent works for the Seller and will use any information you share with them for the Sellers benefit in negotiations. It doesn't cost you anything to hire a Buyers Agent to work for you. It is important that you interview a few agents and choose who you would like to represent you.