Keyword use in Title Tag
Utilizing the targeted search term or phrase in the title tag
Not only is the title tag a strongly weighted factor by Google, but having good titles is also very important for a high CTR in SERPS. And undoubtedly your best chance to catch a searcher attention and convert into a visitor. Another point is that people tend to link to pages using the title as anchor text. Always give attention to titles, just stuffing the title tag full with keywords is bad practice.
Keyword use in Domain Name
Including the targeted keyword in the domain name (e.g. keyword.com)
If the domain name is an exact match and aged than it is strongly weighted by Google. Owners of keyword domains are blessed, not only because of the limited availability from keyword domains, but people also tend to link to pages using the URL as anchor text. In that case is the targeted keyword in every URL.
Keyword use in Anchor Tags
Including the targeted keyword in the anchor tags
Keywords in anchor tags are for some years an important criterion of the Google algorithm. Links from the target site to the target page weight the same as an inbound link from another site to the target page. That's one reason why a good sites link structure is very important.
Keyword use in Body Text
Using the targeted search term in the visible, HTML text of the page
It is important to use keyword phrases throughout the page where it makes sense, but never forget that body text is for visitors.
Keyword use in Page URL
Including target terms in the webpage URL (e.g. example.com/keyword-phrase)
Including keywords in the page URL is not a strongly weighted search engine ranking factor, but the point is that people tend to link to pages using the URL as anchor text. Also having your keywords bolded in the listing URL from the search engines can catch a searcher attention.
Keyword use in H1 Tags
Creating an H1 tag with the targeted search term/phrase
The use of H1 tags is very overrated and often abused.
Keyword use in H2, H3, H(x) Tags
Placing targeted terms in the H2, H3 headline HTML tags
see H1 tags
Keyword use in Images Alt and Title Attributes
Using target keywords inside images alt and title attributes
When an image is used in place of anchor text, the alt acts as anchor text. Alt attributes for linked images do have some importance. It is an important ranking factor for Image search.
Keyword use in Description Meta Tag
Utilizing keywords in the description meta tag in a webpages HTML header
Utilizing a description Meta tag is important for display purposes in the SERPS, and can influence users to click on a listing. The meta description is still used as the listing description for search engines. Having your keywords bolded in the listing description from the search engines can catch a searcher attention. Just stuffing the description Meta tag full with keywords is bad practice.
Keyword use in Bold/Strong Tags
Positioning keywords in HTML text with strong/bold tags
Setting words apart from the rest of the text indicates that they are important, but I haven't seen real evidence to show this as being a real ranking factor.
Keyword use in Keywords Meta Tag
Utilizing keywords in the keywords meta tag
The keywords Meta tag is not used, and has never been used by Google. There is no search engine left who uses the keywords Meta tag.