I am a permanent resident since July 7 of 2011 when should I apply?
You may apply for removal of the conditions on your lawful permanent residence 90 days prior to expiration of your green card. You should include documentation to illustrate that you and your spouse remain married and reside together as a married couple (joint lease agreements, bank accounts, other joint accounts, car insurance, birth certificates for children, etc.). If you and your spouse are no longer together, you must provide proof that the marriage was entered into in good faith and not for the purpose of evading immigration laws and you will need to request a waiver of the joint filing requirement. The timing of filing the I-751 will depend on whether a divorce has been filed, finalized or is currently pending.
Additional information about the time to file Form I-751, evidence to be included, filing fees, etc. can be found in the directions for Form I-751 found on the USCIS website. I have included a link for you below.
There are many documents and evidence that you can submit in support of your I-751. The documentation should be tailored to reflect the true nature of your relationship with a focus on the commingling of your finances. Remember to timely file it; within 90 days immediately preceding the expiration date.