Pick the keywords that are most appropriate to your business – not necessarily the most searched terms.
For example, if “key phrase A” has 3,000 searches per month and “key phrase B” has 500 searches per month, then you might be tempted to choose “key phrase A” to have in your SEO campaign.
The thinking here is that more searches equals more sales.
However, you need to weigh up the benefits of this. If your product or service offering almost exactly matches “key phrase B” then you are much more likely to convert this “Googler” into a client. Thus your return on investment will be maximised.
Keep it simple – choose the keywords that are most appropriate to your business first. Out of these select the ones with the highest search volume.