Some useful ideas for marketing online?

You need to write quality and original content for your site including rich articles and keyword/phrase.
You also need to build a web page with targeted SEO keywords with original content.
These keywords will help your site in getting top ranking in any search engine.

Be specific, choose the channels w.r.t the target audience.
Decide on the budget before embarking on it.
Design content in brief but smartly

Online marketing very useful in engagement with your target audience, so based on your industry you can find the best idea you can engage with them.
Social media and mobile marketing are very crucial in online marketing now and you can engage more consumers using new technologies like Augmented Reality on mobile marketing or online contests on social media.
In addition to main channels of online marketing, setup a content strategy to your brand and don't ignore video marketing it is the number one growing media now online and most engaging one as well.

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Online marketing mainly consist of SEO, PPC & SMM.
For online marketing you can choose any one of these medium to promote your website.
1- For SEO you need to select keywords, create unique quality content and promote your website though content and links.
2- PPC is paid marketing on different platforms.
3- SMM is social media marketing which is actually website or brand promotion on social networking websites.
There are other online marketing types like email marketing, affiliate marketing, video marketing, etc.
Most effective mediums are above top3 which can give good ROI.