Avoid SEO techniques like keyword stuffing, using invisible text etc that are considered black hat SEO.
Keyword stuffing is nothing, but packing your keywords onto the website. If you have a list of keywords to use, do not make liberal use of them in you website. Use tools, which can help you to find the keyword density. Maintain a standard of around 3% to 7% keyword density. Make use of synonyms and make yourself aware of LSI to ensure that you have a good page developed within limits of acceptable use of keywords.
Invisible text is another technique that some SEO try using. It is nothing, but putting a list of keywords in white text on a white background. What it does is that it cannot be seen by readers, but attracts more search engine spiders. This can help get higher search engine ranking for usage of keyword, but again it is unethical to use it. Even the search engine algorithms may consider it, as spamming. Similarly, there is a concept some refer to, as doorway pages. It is basically a fake page that may not be ever seen by the user. It is just created for tracking search engine spiders in an attempt to give them content to index you higher.
It is better to practice white hat SEO, rather than using black hat SEO to score over a competitor, who may be on the top using black hat SEO techniques. Wouldn’t using ethical techniques to rank high be better, than using black hat SEO techniques, which can always keep you under a scanner? Unethical means can surely see your earnings skyrocket in a short term, but may get you banned in the long run. Your aim would be to earn for a long time and there are many ethical SEO techniques out there, which can help you immensely. Be alert to news about the search engine criteria and ensure that you do not end up using black hat SEO. So, if you are thinking of using black hat SEO, to gain that last bit, needed to boost your rankings, think again.
I am sure, you do not want to end up penalized.