Since I don't have much to add to NJGoat's list of above average agent characteristics I will comment on "ideal buyer".
First and most important a buyer has to be able to honestly disclose the PREFERRED amount they have to spend on home, the MAXIMUM they can spend based on honest pre-approval from a reputable lender along with realistic estimates of closing costs and down payment, and not withhold anything about sources of income / downpayment of status of employment.
A buyer ought to have a realistic list of wants / must haves / nice to haves. Without something like this it will be too likely that no existing or newly constructed home will be found in any reasonable length of time.
A buyer must understand the way that comparables are used by qualified listing agents to set asking price, how a similar set of data will help them make an acceptable offer, how lenders will need to have an acceptable appraisal to support any offer, and how each house is likely to sell for an amount close to the average percentages of list-to-ask for an area.
A buyer should be able to find some tangible reasons to dismiss a property -- when the buyer cannot articulate what they "don't like" about a particular home it makes it all but important for the agent to know if additional homes similar / different will have the same objections.
The buyer should communicate to the agent in a consistent and uniform method -- sticking with email or cell phone, not having one spouse / partner using one method while another is communicating via the other keeps everyone on the same page.
Do not involve family members that are not going to be on the title in the process. This means selection, pricing, inspection, and negotiation. If any financial assistance is coming from family members they will have to sign off on that help being a gift, and in the same spirit they ought NOT to attach any "strings" to other parts of process.
If you have kids that need to be supervised leave them with a sitter. Some kids need to be supervised until they are college age...
If you have friends whose opinion you value bring them along before any commitment is made to other parties -- whether your friends think the house is a screaming deal or a rip off matters less than WHEN they express this.
If you want to do research on your own that is fine, but realize why publicly available information might not match what is in MLS or other official sources, and the implications for this, especially that some kinds of free information is not worth what you paid for it
If / when you have doubts about what your agent is telling you LET THEM KNOW so they can either clarify what you think they've said OR give a complete context for the shorthand that they may be using.
Listen to what your agent tells you and repeat it back to them in a way that allows them to know you heard it.