Its getting harder to get decent ranking, mostly because of the huge increase in competition - here's a few of the basics though:
1. Fresh, unique content is what Google loves, lots of it. So minimum 6 pages with a decent amount of text on each of them, ZERO copying & pasting "borrowed" text from other sties, and a blog page that you regularly update with fresh company news & special offers.
2. Use the google keyword tool to find out what relevant keywords are being searched by people in your area - these are usually the names of your services and the names of the towns you work in but regional quirks of language mean that in some places "Window cleaner" is searched 10x more than "window cleaning" - research what your audience search and target these keywords.
3. Make your page titles informative to Google - instead of "Home, about us, window cleaning, contact us" try something like "Window Cleaners in (insert town name), About (area name) window cleaning services, professional window cleaning in (insert area name), Contact (insert area name) window cleaners)" etc etc.
4. H1 and H2 tags have become very important recently - so make sure you use them on every page and take the same approach with them as with your page titles.
5. Meta description tags are used by many search engines to generate the "snippet" that is visible in the search results, so write these tags to be appealing to searchers.
6. If its in your page titles, meta description & H tags, it needs to be in your on-page text too.
7. Dont spam keywords - don't repeat the same keyword more than once every 150 words.
8. Google has gotten very good at distinguishing between content and structure of a website recently, so packing keywords into the page footer doesn't work very well any more.
9. Internal links between pages (Not just the main menu) can really help google to find ALL the pages on your website quickly, so hyperlink any relevant words to the pages they refer to.
10. Submit your site via google webmaster tools, verify it and upload a sitemap.
11. Link your social media business pages to the website, and every 4th or 5th post on your social media wall try including a link back to a specific page on your website
12. Get a google places listing
13. Signup for as many free online business directories as you can find & include your website in the listing
14. Have your web address in ALL your forum signatures and e-mail signatures
15. Make sure your website is smartphone/tablet friendly - over 50% of browsing is now done via mobile devices and if a viewer sees your site isn't easy to view & clicks back to Google this can give you a huge "bounce rate" - Google sees visitors bouncing and thinks your site isn't relevant for that search, so reduces your ranking accordingly,... this is something that is getting more & more important!
There's loads more - but those are the basics,..