How do you maintain web application user experience during development?

Refer to Peter Morville's UX Honeycomb, 7 factors describing a user experience: useful, usable, findable, credible, desirable, accessible and valuable. A product is useful if helps the user to solve a problem or fulfill a need. The product has to be usable. It has to take the user from A to B without interruptions. Make the main taks findable. Put them in front of the user, clearly. Inspire trust, be credible, ensure a proper practice for treating the data. Be desirable, if all factors are equal between you and a competitor, the user will always choose a product that looks and feels good. Accessible, your product have to serve ALL the users. Valuable, if you've respected all the 6 points, you've created value for the user.

Not only you have to follow the standards, but also the untold ones: patterns, patterns and patterns. Users expect a certain kind of behaviour due to the previous experience. Patterns are now established, and have become a formal standard. The hamburger menu has a definitive icon, don't change it. Top menu, footer, are a standard. Paginations for long listing like search results, autocomplete for search, and the list go on. Swipe left or right, standard gestures. The principle is "don't make me think", so don't reinvent the wheel if is not strictly necessary. Any time you introduce a new kind of interaction be sure to explain it to your user, and remember that no one likes tutorial to learn how to use a thing, so be immediate.

Also, refer to Don Norman's three level of design: Visceral, Behavioral, Reflective. Visceral: Get inside the users head and tug at their emotions to improve the user experience, using "the right" picture, a picture that trigger an emotion for your users base. Behavioral: the usability. Think about the pleasure derived from being able to find a contact and make a call immediately on a mobile phone, the difficulty to type on a small phone compared to a desktop keyboard, the engagement of using a responsive and well designed object. Reflective: The user's afterthought. Did I enjoy the experience, would I reccomend it, does it reflect who I am? I love using Linkedin 'cause it reflects who I am, a professional. Do the same for your products.

Remember that tests can be done early, at any stage of your process, so start from the wireframe, you can do a "tree sorting" or a "first-click-testing". A good sequence of testing could be "Survey - Early Testing Design - Usability evaluation - Analytics & A/B Testing & Multivariate testing" While A/B Testing is to check between two (or more) different version of a page, with a multivariate you can differences in the elements of the same page. Then remember there are quantitative and qualitative tests, so decide which one you're in need of. Quantitative gives you a lot of data you have to give a sense, so consider the statistycal significance, qualitative gives less but more aimed data.

That's AGILE. Get the feedback, return to the desk and implement it. The work never ends with the delivery of the product, it continues and it's an iterative one. Schedule the maintainance and the updates as regular process, remove your timelines and prepare a "Now, Next, Later" space. In the "Now" you're going to place what's your actual state (of course) and in the Next you're going to place the things you're going to do right after, while in the "Later" you place the thing that are off on the horizon. Inform your developers and stakeholders, make them aware that there's development required, so they can plan their schedule accordingly, sharing information is key.