For some while it's been pretty clear that reporters have only slim chances of getting useful help from the US EPA press office — or the equivalent at many (not all) other agencies. If you expect nothing from the press office, you will rarely be disappointed. Even getting a callback before your deadline is a major feat. Good stories rarely come from a call to the press office. Of course, there are times when you have to call them. But even public affairs professionals will admit that good reporters do their best to circumvent the public affairs people.
So here are some pro tips:
- Know who you want to talk to. It may be a scientist who has published an article. It may be an agency staff member. Use the EPA locator  and organization charts.  Many agency activities involve Federal Register notices, and almost every FR notice has the name and phone number of an agency employee whose job is to give information to the public. Ask knowledgeable people who the good sources inside the agency are.
- Call up the agency employee you want to talk to. Begin talking to them. Do not begin by going through the press office. If they are reluctant, you may choose to offer them anonymity. If they say they can not talk to you, write that down and make it part of your story. Go to the press office only if and when you must.
- Cultivate personal relationships with regular sources inside the agency. Establish trust — this may take a long time. Convince them that you will go to jail rather than do anything that would identify them. Talk to them when you don't want a story from them. Listen.
- Go to meetings. Agency personnel attend many kinds of meetings. Scientists, for example, attend scientific meetings, and may often present papers at them. But there are many other kinds of meetings, and you can learn about them by cruising agency websites. The social rules at these meetings are different — and sources may often feel free to talk in the hallways or during public Q&A periods.
- Stake out your quarry. Just walking up to someone in a public space and asking them a question can bring amazing results. High-level EPA officials, especially, actually post their public schedules. . (Thank you, Lisa Jackson!) But even lower-level employees may have predictable haunts. For example, if an EPA official is at a Congressional hearing, you might try to talk to him or her during a break or in the hallway.
- Talk to higher-ups when possible. Some EPA Assistant Administrators, who are Congressionally confirmed and often testify on the Hill, are under the impression that they are allowed to take part in public dialogue. You may also find staff in some AA's offices who know everything and will explain it to you on deep background.
- Talk to people outside the agency. Lobbyists, regulatory operatives, scientists, contractors, grantees, Hill staff, people from nonprofit and NGO policy shops, academics, etc. Such people often know more than the media or the public about what is going on in the agency. Trade info with fellow journalists when possible.
- Talk to people at other levels or branches of government. Congressional committees have subpoena power that can pry loose information reporters can't hope to get on their own. Ditto for the discovery power of lawyers in litigation with an agency. State agencies watch federal agencies like hawks to anticipate actions that will affect them. You may find that some people at EPA regional offices sometimes see things differently than people at the EPA headquarters press office.
- Start with documents. Do the research. If you know the subject, this often puts you two moves ahead of the PAO. Know the answers, if possible, before you ask questions. Sadly, this takes time and effort, which is a big part of good journalism. If you are ignorant, you are a pawn of the press office. If there is a docket,  go through or read it before you start making calls.
- File a FOIA request. Yes, the Freedom of Information Act's purpose is to get you records. But in the human and political world of reporting, it also serves to cover the rear ends of people who want to give you information but are not allowed to by the political appointees who give them orders. Once you have established that you and the public have a legal right to the information, sources may sometimes be more cooperative.
- If an EPA (or other agency) employee says they are not allowed to talk to you without press office permission, ask them how they received this instruction, whether it was in writing, and whether they are willing to give you a copy of the directive. Ask the employee why they feel a need to follow a policy which is not in writing. Tell them that the press office says that no such policy exists. EPA maintains that it has no such policy, at least not in writing. If the employee tells you how they got the don't-talk directive, record that, make it part of your story, and contact the WatchDog. 
- The default assumption is that everything is on the record. Never agree to rules of attribution unless they serve your purpose of giving information to the public. An agreement does not exist unless and until two parties agree to it. PAOs can not assume that they are on background unless you agree. They get the big bucks for being "public" affairs officers. Make them earn it. Quote them when they say "I can only talk to you on background." Then ask them why. Then quote their answer.
[Ed. Note: There are a few federal press offices that actually are trying to help you. For example, the US Geological Survey, or parts of NOAA such as the National Hurricane Center. When they help, give them hugs.]