Some marketing and PR strategies are purely proactive; they exist outside of any inciting event, and serve as the first link in a chain of reactions, such as a new ad campaign with a novel concept. Others are purely reactive; they exist as a response to an external stimuli, such as a press release addressing legal allegations.
When it comes to SEO, the majority of your actions are going to be proactive. SEO is a slow-moving strategy that revolves around pillars of brand consistency and reputation building; reactive strategies really don't have a place here, at least not in the purest sense. However, there are some critical moments and opportunities that you can take advantage of for the health of your SEO campaign. Think of these as hybrid reactive-proactive strategies that require an initiating event to get started:
1. Low (or no) competition keywords.
Keyword research and keyword-based optimization strategies have evolved significantly ever since Google's Hummingbird update and obfuscation of keyword data was implemented in Google Analytics. Keywords are no longer associated in the kind of one-to-one relationship they used to support, but there are still positive associations between keyword phrases and user queries, so it pays to do your keyword research.
Keep an eye on search volume and competitor rankings for a range of different keywords. You don't have to be exhaustive here, but you'll want to pay attention and cycle in new keywords every few months. Every once in a while, you'll stumble upon a keyword relevant to your business with significant volume and little to no competition--when you do, it's your time to strike. Work on a new article or piece of content focused on that phrase, publish it, and publicize it to earn inbound links and shares. With the SEO world as crowded as it is, these competitive opportunities are rare.
2. An under-covered topic.
Equally rare is finding content topics that haven't yet been covered, or have been covered unsatisfactorily elsewhere. The former are extraordinarily difficult to find; since they aren't being publicized or talked about, you'll have to rely on some primary journalism techniques, and possibly your own intuition to discover them. The latter are somewhat easier to find, as you'll read them and think, "I can do this better."
In either case, you have a time-sensitive topic that people want to read and no other immediate competition. Even if your topic isn't time-sensitive, there's still a ticking clock on your efforts, as it's only a matter of time before someone tries to beat you to the punch. Being the first on the scene with a new idea or coverage of a new topic can be highly valuable, and will give you a boost in visibility, reputation, and inbound links.
3. A guest posting opportunity.
Every guest posting opportunity you get is valuable, so consider each carefully as you receive offers. You might interact with an editor of a publication on social media, or discover that one of your contacts got in at a new online magazine, or you might even be propositioned directly by the publication in question. In any of these cases, don't turn down the opportunity to get yourself published--you'll earn a link, a potentially recurring outlet (and new audience) for your content, and build relationships.
There are only a couple of caveats to this. You won't want to take a guest posting opportunity with the potential to decrease your authority, such as one from a low-authority source or one completely unrelated to your industry. Use your best judgment here, but don't look the gift horse in the mouth too closely.
4. A newsworthy event.
Is your company announcing something significant? Are you hiring new team members? Expanding the business? Launching a new product? Doing something noteworthy in your community? These are regular elements of any business, and most small businesses just let them happen. Mid- to large-sized businesses know never to let an opportunity like these slide past.
This is a critical chance for you to write up and submit a press release. As long as your write-up frames the story as newsworthy (and conforms to formatting standards), you can count on some news sources picking up your story. Most of these will come with inbound links, and they'll all represent brand exposure, brand mentions, awareness, and improved branded search results.
5. A competitor's new strategy.
Watch your competitors carefully, and be prepared for any opportunity to strike with a counter-strategy. For example, let's say your competitor is launching a new content campaign that focuses on a specific subset of your shared demographics. Can you respond with an even more targeted or more detailed strategy that targets the same niche, effectively one-upping them? Can you take advantage of their distraction by targeting a different niche altogether? Any reactive approach here can yield a benefit; only by doing nothing do you gain nothing.
These opportunities don't always come up, and they're somewhat out of your control, so it's on you to pay attention to how and when they develop. When they crop up, you have a limited window of opportunity to engage with them, and if you miss that window, you'll miss your chance to strike. None of these opportunities, alone, will make or break your campaign, but if you consistently address these situations when they come up, you'll add to your search visibility.