Choosing the right theme for your WordPress website is actually surprisingly difficult. There are so many themes out there and it is easy to feel overwhelmed by the sheer number you'll have to sort through. Another complication is that since themes are made by different makers, there isn't a standard way of describing what features they include. Don't assume that you can customize everything (colours, fonts, page layout) - it's only recently that themes are becoming more and more customizable. So, do read the small print and check that you will be able to do what you want to do with the theme you have chosen.
Here are some tips to help you find the right theme.
1. Know that it will take you some time, perhaps even a few days, to find the right theme.
Set aside the time for this and be methodical. Take notes and screenshots to help you remember which ones you liked, and copy the URLs of the themes you like as a reference, so you don't have to hunt for them all over again.
2. Be very clear about what your needs are.
Several of my clients have bought a theme that they have immediately liked, perhaps because some of the dummy content resonated with them or they liked the overall style, and then have realised it didn't correspond with what they actually needed. If your site is a business site, don't choose a photoblogging theme no matter how stylish it looks, and if your site is a blog, don't choose a portfolio theme that showcases portfolio elements on the front page, when what you want is to show the blog posts up front, and don't even need a portfolio.
3. Choose a theme that already looks as much as possible as you'd like it.
It's really worth spending time finding the right theme to avoid having to pay a programmer to change the code once you've bought it, because it isn't quite as you wanted.
4. Don't assume you can customize the theme. Read the small print and check you can change the page layout and change the colours and fonts, if you want to. If in doubt, ask the theme maker.
5. Don't be put off by the dummy content that is on the demo site for the theme.
I've seen people put off by the stock photos they see on the demo, but of course, it'll look quite different by the time you get your own images in there. So, only take into account the elements that won't be changed.
Free or Premium?
In general, I'm a big advocate for premium themes. If you think about the importance of the image your website presents, it seems to me that the small, one-off investment you make when you pay for a premium theme is absolutely worth it. They look so much better! Also, you'll get a good level of support with a premium theme, which you may not get with a free one.
That said, it is true that not everyone has budget allocated for a premium theme, especially if you are launching a site as an experiment or you are just playing around with an idea.
A tip for browsing free themes
Your WordPress website will come with several free themes installed - which ones they are depends on your host. You can browse these, and activate them easily by going to Appearance > Themes. But there are many more available than just these - click on "Add New" and you'll see a large selection of other themes you can install just by clicking the blue "Install" button that appears when you mouse over them.
It's very useful to see the screenshots of the themes because this gives you a taste of what the themes will look like once they've been set up - you can't see this as easily if you just install them and preview them on your own site. But you can't really see how a theme has been designed to look when it's all set up without looking at a live demo of the whole website. To do this, note the name of the theme you're interested in and go to the WordPress Free Themes Directory (here). Then search the theme by name; when the theme comes up as a search result, click on its title. To the right hand side of the page, click "Theme home page." This will take you to the theme maker's own website and there will usually be a fully set up live demo for you to look at; in addition, depending on the theme, there may also be setup instructions, support and FAQ available for you to consult.
The best places to get premium themes
Finding the perfect theme may feel like an overwhelming task - I sympathise. I totally felt the same when I first got into WordPress. Here are some of my favourite places to get premium themes, which may save you some time.
ThemeForest There are literally hundreds of themes available here, from dozens of different theme makers. Choose the category you need e.g. Blog/Magazine, Corporate, or Creative for portfolio type themes, or look at Popular Items. ThemeForest is your best bet for a corporate looking theme - though they have all kinds, including many trendy one-page themes.
Creative Market This is another marketplace selling themes from different makers - there's a particularly nice variety of quirky, blog-type themes available.
Organic Themes Very nicely designed themes for all kinds of sites. The dummy sites are highly customised - you can change most of the elements. Take a look at the showcase to get some inspiration and to see how different the themes can look.
WooThemes This company is responsible for developing WooCommerce, one of the most popular WordPress e-commerce plugins available - they have really nice modern-looking themes for all kinds of site available, however, not just e-commerce.
WP Explorer This is a curated collection (many drawn from ThemeForest, which can save you some time hunting), with some of their own - these are particularly good and there are also many very nice looking portfolio/blog-type free themes available, and many business themes.
Dessign A beautiful collection of stunning themes for creative people - many especially for graphic designers, artists, etc - all with a visual emphasis and most containing portfolios.
ThemeTrust Design-led, minimalist themes, with a focus on portfolios for creatives - photographers, designers, etc.
Graph Paper Press One of the most famous providers of themes for photographers and other creatives.
Bluchic Beautifully designed blogging and e-commerce themes with a feminine feeling.
AngieMakes Another good source for pretty, feminine, on-trend blogging themes.
How to upload a premium theme
To upload a premium theme, go to Appearance > Themes, click "Add New," then "Upload Theme." Browse, upload and activate your new theme; it needs to be in .zip format (make sure you are only uploading the theme, and not the documentation at the same time - the theme won't work if you accidentally do that).