You can still of course find job ads in all the usual places, including newspapers and magazines, shop windows and noticeboards in your local area. However, the Internet has fast become the go-to tool for recruiters, because it allows them to reach a vastly wider audience than print ads in next to no time and for a fraction of the price. Employers post job ads on their own websites, with online recruitment agencies and on dedicated job sites. You may also find them advertised on professional networking platforms, discussion forums (where etiquette allows) and even social media sites.
Ask colleagues, peers and friends (we’re almost all workers, after all) which general and specialist job sites they've used or search for online user reviews. Visit a bunch of recommended sites to see which ones work for you. Don't limit yourself just to the biggest and best-known though. There are sure to be smaller niche job sites focused on your geographical area and employment sector that will list vacancies relevant to you.
All decent job sites these days have extremely effective filters to allow you to narrow down your job search on the basis of location, salary, sector, skillset… you name it. Save your preferences and set up an email alert so that the site keeps searching for you and let's you know as soon as anything suitable comes up.