How to optimise SEM campaigns

The techniques that separate campaigns that burn budget from those that deliver profitable results

10 min

Launching an SEM campaign is relatively easy. Optimising it to be consistently profitable is the real challenge. The difference between a campaign delivering 2x ROAS and one delivering 8x lies in continuous optimisation: reviewing data, making informed decisions and tweaking every variable.

This guide covers the most effective optimisation levers: from quality score and negative keywords to advanced bidding strategies, ad testing and landing page improvement.

Quality Score optimisation

Quality Score is the variable with the greatest impact on campaign profitability. A high QS lowers the actual CPC you pay (you can pay up to 50% less than competitors) and improves your ad position. Optimising it requires working on three fronts simultaneously.

Improve ad relevance by ensuring the copy contains the keyword and matches the search intent. Optimise the landing page for speed, relevance and an excellent user experience. Boost CTR with more compelling headlines and extensions that expand the ad.

  • Organise campaigns into ad groups with 5–15 thematically coherent keywords
  • Write at least 3 ads per ad group with the keyword in the headline and description
  • Dedicated landing pages per ad group, not one generic page for everything
  • Monitor QS by keyword and prioritise those with the highest spend

Negative keyword management

Negative keywords are just as important as positive ones. They prevent your ad from triggering on irrelevant searches that waste budget without generating conversions. A search terms report reviewed weekly is the primary source for identifying them.

Create shared negative keyword lists at account level for terms that are never relevant (free, reviews, jobs, DIY how-to) and campaign-specific lists for terms relevant in one context but not another.

  • Review the search terms report weekly
  • Create negative lists at account and campaign level
  • Exclude informational searches if your objective is transactional
  • Add competitor names as negatives if you don’t run conquest campaigns

Advanced bidding strategies

Google’s automated bids (Smart Bidding) use machine learning to adjust bids in every auction based on conversion likelihood. To work well, they need sufficient data: a minimum of 30–50 conversions per campaign per month.

If you lack enough conversion volume, start with Manual CPC or Maximise Clicks to gather data. Once you have volume, migrate to Target CPA or Target ROAS. Adjust targets gradually (10–15% changes) and give the algorithm 2–3 weeks of learning between changes.

  • Target CPA: when you want to control cost per conversion
  • Target ROAS: when you have varying conversion values and want to maximise return
  • Maximise Conversions: when volume matters more than unit cost
  • Use bid adjustments by device, location and time of day based on performance

Ad testing

Responsive search ads (RSAs) allow up to 15 headlines and 4 descriptions that Google combines automatically. But this doesn’t replace structured testing: you need to test clear hypotheses about which messages resonate best with your audience.

Alternate between different value propositions, calls to action and headline formats. Measure by CTR and by conversion rate, because an ad with high CTR that doesn’t convert may be worse than one with moderate CTR and high conversion.

  • Test different value propositions: price, benefit, urgency, social proof
  • Pin key headlines to control what appears in important positions
  • Measure by conversion, not just CTR: a click that doesn’t convert is a cost
  • Run ads for at least 2–4 weeks before declaring a winner

Landing page optimisation

The landing page is where your SEM investment turns (or fails to turn) into results. A slow, generic or misaligned landing page destroys campaign ROI. The coherence between keyword, ad and landing page is the factor that most influences conversion.

Each ad group should point to a landing page specific to that search intent. The page should load in under 3 seconds, feature a main message aligned with the ad, a clear CTA above the fold and trust elements (testimonials, client logos, guarantees).

Key metrics and optimisation cadence

The metrics you should monitor go beyond CPC and clicks: CTR by ad group, conversion rate, actual CPA vs target, ROAS, impression share and quality score. Each metric signals a different problem and a different action.

Establish an optimisation cadence: review search terms and negative keywords weekly, analyse ad performance every two weeks, review bidding strategy monthly and conduct a full account audit quarterly.

  • Low CTR: review ad relevance and extensions
  • High CPA: review landing page, negative keywords and bids
  • Low impression share: increase bids or budget if conversions are profitable
  • Low Quality Score: improve keyword–ad–landing coherence

Key Takeaways

  • Quality Score is the optimisation lever with the greatest CPC impact
  • Negative keywords prevent budget waste on irrelevant searches
  • Automated bidding needs at least 30–50 monthly conversions to perform
  • Ad testing should be measured by conversion, not just CTR
  • Keyword–ad–landing coherence is the key conversion factor

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