Easy. Make an offer to the owners.
However, if the house is listed with an agent, you're not bypassing the listing agent. The listing agent is already there. Even if you make the offer directly to the owners, they'll consult with their agent. The only way to completely eliminate agents is to find a FSBO (for sale by owner) and then you make an offer without the use of an agent. That way, no agents are involved.
You notice the (justified) scorn of the other agents here. Let me try to clarify something--a surprisingly common misconception among buyers. The misconception is that if you don't use an agent, you'll get a better deal because the commission will be lower and you'll receive some of those savings. That's incorrect.
If a house is listed with an agent, the commission is already set. The homeowner, in 99.99% of the cases, has agreed to something like: "If my house sells during the listing period, I agree to pay my agent a 6% (or 5%, or 4%, or 7%, or whatever--it's fully negotiable) commission."
That deal's already cut. Whether an offer comes in directly to the listing agent, or whether there's a buyer's agent, or whether you make an offer directly to the owners, the commission doesn't change. It just doesn't. So let's say the seller's agreed to a 6% commission on a $100,000 listing. That seller is going to pay $6,000 in commissions regardless of how the offer is made. The seller won't save a penny if a buyer writes up an offer himself and personally hands it to the seller.
Some buyers think that if only one agent is involved, the commission is cut in half. Not true.
So if you have some fear or hatred or absolute mistrust of agents, you can present your offer directly to the buyers. (Though please have a lawyer review the details.) No problem. Just understand that it's not saving you or the seller a penny.
Hope that helps.