Assuming you already asked about the basics like which bits of the site can be edited, what other services are on offer, and what levels of support are available, here are some important things to know before signing on the dotted line..
1. Are They Actually Developers?
We think this is the single most important question to ask. Believe it or not, there are some so called web designers who only use a website builder (like Adobe Muse - and - yes we've seen it - Dreamweaver!) and they wouldn't know what to do if you suddenly decided you needed parallax images on the home page, or if something broke - other than Googling it and hoping somebody else has posted a fix. A developer will code your site up using modern industry standard languages, and your website will be more portable and much lighter on it's feet as a result.
2. Is it Wordpress or Joomla or Drupal?
There are some ups and downs with Wordpress (see here) but Joomla and Drupal are BIG no-no's. Either way, question one still applies because Wordpress can easily break if a plug-in developer doesn't keep up with the Wordpress updates, or other plug-in updates that it relies on. We've seen plug-in developers disappear leaving the customers high and dry.. What then? Somebody has to get their hands dirty with the code.
So if you're going with Wordpress just make sure that A) they've got some development credentials, and B) any licensing costs for plug-ins are included in the quote - with renewal costs - because they can be a killer.
3. Is it Linux or Windows?
If they say Windows start running, and don't look back! Microsoft do one or two good things, I'm struggling to think of them off the top of my head but their web development sytem ASP.NET definitely isn't one of them. We've had lots of quote requests over the years but a couple stand out because they specified "No ASP.NET". Microsoft love to complicate things, you may have noticed, and they really went to town with ASP.NET, it's almost universally hated - and it has no place for small to medium sized web development.
4. Is it Generically Mobile First?
Sounds complicated (or obvious depending where you're at) but all it means is does the website serve up a second version of the site for mobiles, or does it just have one version that adapts itself to various devices? You want the latter. One version that adapts, it's called 'responsive', and some webite builders (like Adobe Muse) will often dish up a whole different set of pages for a mobile. What you're looking for is a "Mobile First" framework for your website.
5. Who's Hosting?
Hosting is the only thing more important than what your website looks like or what it can do, because a badly hosted website wont even be visible some of the time, and/or slow. And both those things are not only bad for you and your visitors, but bad for Google, so your search rankings will suffer - a lot. So if it's any of the following.. Heart Internet, 123-Reg, Webfusion, Mesh Digital, or GoDaddy then proceed with caution because they're all Host Europe Group companies - actually they're all GoDaddy companies now since they acquired HEG in 2016, and to be fair we only have first hand experience with Heart Internet which went right down the pan when HEG bought them out. To put it politely.
You need proper developers, using industry standard Linux based techologies with modern mobile first development techiques and hosting on modern, flexible and fast UK based cloud servers. Somebody who does all that at very low cost and you can phone for help and advice and actually get through.
Oh hang on - we know somebody who does all that!