effective method of bidding cpm or cpc

CPM and CPC both methods have its own merits and demerits. CPM bids are kinda cheaper than CPC bids. Hence when you are sure that your CTR’s will be very high, then it makes sense to go for CPM based bidding. Mostly the offers kinda campaigns are done using google display with CPM bidding.
For Example: Uber’s/OLA’s first free ride campaigns.
At other end when your objective is to get actions then it makes sense to go for a CPC based bidding strategy. So that you pay for clicks and clicks come when there is an intent.

It depends on your business, keywords and ad copy. Most of time CPC is better.

CPM and CPC both methods have their own merits and demerits. CPM bids are kinda cheaper than CPC bids. In most cases, people will generally use CPC bidding as it is designed for the Search Network. It’s also the recommended bidding strategy when trying to drive traffic to your website and you know how much you are willing to pay. CPM bidding is the most common option for advertisers who are targeting the Display Network as this is the best option if you are trying to increase or improve your brand visibility. CPC bidding is mainly used for Search Network campaigns and CPM bidding is primarily used for Display Network campaigns.