A new project at work

Today at work my boss told me to join in a new project with a partner to program a point of sale (POS) in Java SE that is the language i know better, but now i need to plan all the project (yes, make estimations times, activities charts, select development methodologies and further more.)

Honestly i don't have any experience in projects planning but in this post i'll make a list of things that im pretty sure i need to do (you could help me if u see something is missing), in this way, i'll make an scalable project that i'll endure by the past of time (we have already the app specs so i'll pass that step).

1st Activities chart

Is important to make this, in order, to divide the projects in parts and attack those parts one by one like the saying "divide and conquer"

2nd Iteration's plan

After we have our activities we could make an estimated number of beta releases to be sure that our work is going ok and to know new specifications about this app that the client would have missed before, in this way, we could measure either the time we will spend making this project and establish a tentative date when the project will be finished (these phases are fundamental in agile development).

and 3rd (but not less important) Selecting design patterns and code rules.

Having our activities chart, app specs, iteration's plan we could start to think how will we code our app having in consideration that we wont be forever in that project and future programmers could take our code and improve it, is important to select design patterns to make sure that our projects (like i say before) will be scalable by the pass of time, and future programmers will easily make changes on it (our app), having in consideration all the things written before we could thing in MVC pattern that will help us make a wonderful scalable app that ill easily modified and understable.

The code rules will be focus in how will we code to make the code easy to read and easy to refactor that is important.

After having all of these steps in our project i will think "Okay now we are ready to code"

P.D if u have another thing to add be free to post it ;D (sry if my english is a little bad im foreign)