There is no doubt for me that SEMRush proviedes the most comprehensive set of SEO tools. Almost all areas of SEO are covered, KPIs are tracked, advice given and recommendations made.  It's expensive but very good.
https://www.semrush.com/ 

There are plenty of SEO tools available that cover different areas of SEO such as keyword analysis, site checker, link building, competition spying, local listing and SEO-friendly content ideas. It really depends on what you need to do with your SEO. Some tools are all-encompassing while some only offer one area of SEO. 
 
But here’s a list of the top or best SEO tools out there.
 

• Google’s full suite of products – this is the granddaddy of SEO and they offer a whole host of software and apps to help your SEO. All of them are free. Google Analytics help analyse your site traffic and user behaviour. Google Ads’ keyword planner tool is great for keyword research and analysis. Google Trends is another that analyses search trends and you can filter based on countries, duration and others. Google Search Console is a webmaster tool that highlights SEO issues on your site as well as monitor organic keywords.
• SEMRush – you need to pay for this if you want to unleash its full potential. SEMRush is a really good all-in-one tool that helps with site audits, improving your site’s SEO and content, spying on your competitors, keyword research, link building and generating SEO friendly content ideas.
• Moz – this is another all-in-one solution and they have been around for a long time.
• Afrefs – Ahrefs is another big name for SEO tools. They offer the complete SEO solution and their link building and off-site SEO solution is claimed to be one of the best.
• KWFinder – A wonderful and easier to use alternative to Google’s free Keyword Planner. Get long-tail keywords and ideas for your keyword research.
• WooRank – easy tool to analyse your site and other site’s performance and ranking
• Yoast SEO plugin – this is one of the best tools if your website uses WordPress. Manage your on-site SEO in an all-in-one plugin.
• Answer The Public and Buzzsumo – these two are for generating content ideas and for expanding your keyword research. Answer The Public which is free gives you related terms to a keyword to create SEO friendly content, while BuzzSumo also shows you the top performing content based on keywords.

I'll be fairly brief on this one. Small business needs to understand SEO to the extent that knows enough not to be hoodwinked and to make sure that value for money is obtained. A small business needs to steer his/her company's SEO efforts and speak the language. 

However, in my view as a business manager of many years, (not as a purveyor of SEO services which I now am), business owners should be spending his/her valuable time on running their businesses, not on:

1) Doing their own accounting
2) Fixing their own cars
3) Doing their own electrical and plumbing maintenance
4) Running SEO campaigns
5) Designing Websites
6) Doing their own legal work
7) Doing window repairs
8) Painting and decorating
9) Doing  graphic design

Those things are all needed by a business, but they are services that are best outsourced - especially the complex, technical ones.  Most people would never waste their time and effort learning how to do their own legal work or accounting, but many happily jump into web design and SEO - why? Here are some reasons:

1) They think it's easy because they have been told it's easy - but it's not, not if it's done properly. Done poorly, it's just as effective setting fore to your money - same result.
2) They don't trust anyone to do it for them - and very often I don't blame them. the number of amateur  cock-up artists out there is appalling - we have met many of their victims.
3) It's 'too expensive'. These are often the people who have been the low cost route and suffered. In SEO, most competent suppliers:

a) Analyze the business in question
b) Design a campaign from the various elements needed
c) Track and report monthly process.
d) Make changes as required
e) Remain transparent at all times.

A good supplier will work at a gross margin on purchased SEO products and use the gross profit to fund his/her own monthly efforts for the customer. This is where you MUST BE CAREFUL: With an honest SEO supplier, around 50% - 80% of the customers' money will be spent on agency purchases of SEO campaign products and the balance is what pays the agency for its professional expertise and time in reporting/guiding the campaign - and that's good value.  The lower quality agencies simply keep around 80% of the money and spend very little on SEO product for the customer.  You MUST KNOW WHAT YOU ARE GETTING FOR YOUR MONEY.

So, summarising:
1) if you have the time to become an SEO expert, then go for it and investigate the plethora of tools and services available.
2) if you don't have the time, then do some general reading on SEO and find a reputable agency that you can trust.
3) Speaking as a businessman, you are better off spending time on your business than dabbling in SEO.

Many people will dislike me saying these things and say 'Oh but he's conning us because he wants to sell SEO'.  All I can say is that this is a businessman's opinion, not just that of an SEO seller and i am sincere in what I have said.

I wish you all well in your online journeys; may every one of you find success.
LOL - I said I'd be brief!






 

Indeed, Hatty. And then their online investment sits there like an oasis in a desert wih no roda-signs, no map references, sealed off from the world in spendid isolation!

The obvious choices such as Ahrefs and SEMRush have already been mentioned but I'm mindful that for the small business, these can be pretty expensive. 

Thankfully there are cheaper options, in fact, I'm going to concentrate on free options....

Why not start with Google and @Aishah Mustapha listed great places to start of which I'd like to add Google My Business which is crucial for the local business. Also, more recently for the small online retailers, make sure you get yourself a Google Merchant Centre account and submit your product feed so you can get your products in the free Google Shopping listings (Surfaces Across Google).

But beyond the tools, don't underestimate the power of using Google's search engine itself. Want to rank for a keyword? Type it in. You'll be able to identify the top-ranking results and by way of this you get to understand:
- What Google believes the user is looking for (so you can address their questions/intent)
- The content the top-ranking competitors have, how it's structured and the sub-queries you should address
- You can also see the publish date of the top-ranking pages. If it's all within 6 months and the page you expect to rank is 3 years old then it may be hard, so get in and optimise the page and change the publish date. 
- The other SERP features that you could optimise for. For example if there is a featured snippet, People Also Ask feature or the Local Pack. 

Aside from Google, there are other tools such as:
- Keywordtool.io - Find the keywords you should target.
- Ahrefs Webmaster Tools - ahrefs.com/webmaster-tools - Ahrefs just launched this free tool and it's terrific to give you a picture of your site's health and how you can improve it. 
- GMBSpy - chrome.google.com/webstore/detail/gmbspy/hijfnlgdhfpmnckieikhinolopcolofe - If you want to improve your Google Maps/ Local Pack results, it's important you have the right categories. With this Chrome extension you can uncover the categories your competitors have selected. Match them. 

Hope that helps. If you're looking for more advice on doing SEO yourself, check out this post from Matthew Woodward https://pocketinsights.io/diy-seo/

Would love to get your thoughts on this @Keith Rowley @Quentin Aisbett @Meng Lin @Paula Glynn