Press Release Without Permission
From my experience releasing a press release about your business relationship with a company you are working with without written permission can seriously jeopardize that relationship. Check with the company you wish to write the press release about, even if you are casually mentioning them and especially when you are introducing them as a client.
Most businesses spend years perfecting and then protecting their brand awareness and aligning your company with them in the media, by writing a press release, without their express written permission can be seen as a breach of trust that can easily cause you to lose the client.
Never assume and always ask first and then get it in writing. It will save you writing letters of apology, making phone calls asking for forgiveness, asking for retractions and generally consuming your time you should be spending to cultivating new business. Even if they say no, they will respect you for taking the time to ask. And who knows, they may even say yes and give you a quote. 
