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Steps to take:

Test - Strategy:

Understand - try to understand the main points of the question ( read throw more than one time, if needed)
Eliminate - remove Answer that are 100% wrong in your point of view
Evaluate - think about the tradeoffs of the remaining answers. Consider what is said and what is implied.
Select - select the correct answers (from your point of view; you will never be asked to select more than 2 and if you need to select more than one, the question will ask for it).
Validate - check if your answer corresponse and fulfil the requirments of the given question

Test - & Certification Domaintopics:

Look always for caching options (ElastiCache)
Know how and where to use autoscaling
Selecting the best instance type (t vs m vs c) in regard of the Use Case (Compute, General Purpose -> Webserver vs. App - Server)

Lock down Root - Account
Security Group (doesn't have a dedicated deny state - stateless) vs. NACLs (Network Access Controll List - statefull)
IAM Roles are in a security prospective always the right way to go

For always on instances -> reserved instances is a good optins
Serverless (Lambda, DynamoDB, S3, Fargate) is always the most cost effective option
Selecting the best instance type (t vs m vs c) in regards to Costs
Select the best cost effective storage type (gp2 vs io1)
Cost Optimization Questions -> in most Cases you have 2 Options that will work, but one fits better in regards to costs.