Whether you're new to Google Ads or you're just new to using Maximize Conversions Bid Strategy, you're probably a little scared leaving it all up to Google's bidding algorithm to just 'figure it out' and generate good results for your campaign.
I used to feel the same way. I was taught to optimize a campaign using Manual CPC/Max Clicks Bid Strategies and that's it. I too thought that using one of the smart bidding strategies required me to relinquish all control over the campaign.
Turns out I was completely wrong! While it's true you can only make bid adjustments at the Device level and only if it's -100%, you can still EXCLUDE dimensions that are leading to a high cost and little to no conversions.
Dimensions like age, gender, houshold income, location, ad schedule and of course device.
With location and ad schedule, it's important to set them up as granular as possible so it's easy to spot the locations, days and times of day that are resulting in a lot of wasted ad spend and so you can then EXCLUDE them from the campaign.
You can also of course pause keywords, match types and different ad variations that are also resulting in a high cost with little to no conversions.
I try to group my keywords into tightly grouped ad group themes as well. This helps you to write more targeted ad copy for the set of keywords and help you spot keywords that are, you guessed it, leading to a high cost with little to no conversions.
With ads I like to have them rotate indefinitely, not optimized for conversions. This way I can review the performance for each ad variation myself and determine which to pause or not pause.