Disclaimer: I do eng hiring for startups so my advice will be based on startup experience. Big, established organizations may do things differently.

I would try to keep your resume as concise as possible without sacrificing readability. Sometimes, this means you will go over one page, especially if you’ve been working for a few years. It’s not the end of the world. I would rather see a 2 page resume that looks like it was written by a functional, thinking human being than a one page resume that lacks any kind of content or soul. Try not to go over 2 pages, though, as your reader’s attention span is short. In other words, you should be aware that the people reading your resume are not going to read everything. Make it easy for someone on autopilot to internalize the most impressive things you’ve done, and always err on the side of conciseness. This means that you probably should:

• Refrain from listing every project you’ve worked on. Pick the ones where you took some initiative, built something from scratch, or had major impact on the final product. At the end of the day, I’d rather see one impressive project than 5 projects where you upgraded some framework or followed detailed instructions to fix a subproblem of a subproblem of a subproblem.
• Explain what you did in plain English. I can’t harp on this point enough. People outside of your company aren’t going to know what any number of internal acronyms or tools are. Think big picture. Ask yourself, “Why does what I worked on matter? How did I contribute to the overall mission of the organization? What is the context for what I did?” and so on. This doesn’t mean you shouldn’t go into technical details (you should), but it does mean that you shouldn’t use obscure terminology or the languages/tools/frameworks you used as a crutch.
• Don’t keep repeating what tools/languages/frameworks you used. This wastes precious space, and in most cases, what you did trumps what you used to do it (unless you did something very specific like migrate from one language to another or fix a bug in some framework). Rather than going on about how you used Hibernate to do ORM or whatever (this is a particularly poor thing to go on about because you’re not adding any value — you are using a tool for its intended purpose!), just put all the things you used/know in one concise Skills section. For bonus points, delineate which things you’re very proficient in, which ones you know pretty well, and which ones you’ve used but would need a refresher on before diving in.

To illustrate these points, here are some project descriptions (taken from real resumes). My comments on the bad ones are italicized. I think the good ones speak for themselves.

Bad ones:

Designed software application including: data modeling, software architecture design, software- hardware integration, user interface design, and database management

I have no idea what the candidate did or how he contributed. This is super vague and uninspired.

Developed [product name], using C# in .NET framework, for marketing and allowing end-users to experience [another product name]

Again, I can’t tell what the candidate did. He’s hiding behind products/technologies to potentially mask the fact that he is either not too excited about his work or that he didn’t contribute much.

Good ones:

Created and launched a service that collects product opinions and recommendations from Twitter. The service finds related tweets, removes spam, analyzes sentiment and creates a structured database of everything that was said about particular products [link to demo]. The service is exposed as a consumer website and as widgets that can be embedded in online retail websites.

Evaluated and identified [OS name] network stack performance bottleneck in latency, system jitter, per-packet processing overhead, and scalability of different network IO models through various system measurement and profiling techniques

Note: This post was adapted from an answer I wrote on Quora.