If I put my PMP hat on, the answer looks like this:
1. Identify & Sequence Activities: identify project activities and their relationship (predecessor, successor, etc)
2. Estimate Activity Resources: estimate resources (people, equipment, etc) and quantities
3. Estimate Activity Durations: estimate hours/days for each activity
4. Develop Schedule: create the project schedule (using all the above)
Also, you can Google "top down estimating", "bottom up estimating", "three-point estimating", "parametric estimating", "fast tracking", "crashing", "delphi method", "resource leveling", "network diagrams", etc.
More importantly, this is what real-life (10+ years managing projects) taught me:
1) Never estimate something you don't understand. A few poor estimates can throw a whole project off track. Instead, talk with experts and truly understand what you are estimating.
2) Never schedule or estimate the entire project by yourself. Scheduling is a team sport; therefore, all key stakeholders should be involved.
3) Contingency is never optional. You will run into unexpected issues, so make sure you have a buffer.
4) Always listen to your gut feeling. Especially, when scheduling high-risk projects. If you don't feel good about it go back and re-evalute.
Side-note: Try to remember Mike Tyson's quote "Everyone has a plan until they get punched in the mouth". Projects are the same, your beautiful (well planned) schedule may get punched in the mouth and you will have to re-adjust. With that in mind, planning is important, but execution is everything.
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