I’ve noticed in my flesh a very simple indicator of selfishness: 

An annoyance in myself when being interrupted by people.
For example: I’m at work in the middle of working on an important project and I suddenly get a phone call from someone who frequently needs my assistance.  Or I’m walking through the hall about to leave work after a long day and someone pulls me aside to ask a long-winded question or have a full conversation.  Or I’m at home in the middle of something that seems important and my children suddenly become hungry and start asking for me to get them some food.  These are interruptions that tempt me to give in to selfishness.
Outwardly the temptation is to snap back with some excuse (which at least sounds genuine) why I do not have time for that person.  Inwardly it is to say to myself things like, “I have other things I have to do, can’t I just get one minute alone, I’m in the middle of something important.”
When I saw in myself an unwillingness to be interrupted (that is, an unwillingness to be generous with my time), I felt the Lord speak a simple, gentle word to me: “If you really want to be like Jesus, you have work on that.”  Then I thought about how generous Jesus was with His time and how willing He was to be interrupted by people because He loved them so much, and was fully freed from selfishness.  For example:
Matthew 14:13 “Now when Jesus heard about John, He withdrew from there in a boat to a secluded place by Himself; and when the people heard of this, they followed Him on foot from the cities. 14 When He went ashore, He saw a large crowd, and felt compassion for them and healed their sick.”
At one of the rare moments when it seemed that Jesus really needed a moment to Himself (to mourn John’s death), the people continued to follow Him and would not leave Him alone.  He did not try to evade them or run away faster than them (He could have even called a legion of Angels to carry Him away to be alone!)  Instead, He had ‘compassion’ on them and healed their sick – plainly and simply, He put others before Himself.  He was grieving immensely to lose one of the people He loved the most, and instead of demanding some time for Himself to mourn, He gave Himself over to serve others.  Now that is an unselfish man!
It's not that our Lord was a push-over who always let others determine what He was doing.  There were times when He didn't jump right away for the needs of others because it wasn't God's will for Him.  For example in John 11 when Mary and Martha sent word to Jesus that Lazarus was very sick.  Jesus didn't go to him right away (because He was listening to the Spirit's guidance), and Lazarus died.  But eventually He did go and then He raised Lazarus from the dead, bringing many people to believe in Him (John 11:45).  It's not about always doing what other people want, but about having the willingness to put their needs above our own (when God calls us to).
My goal and my prayer is to be like Jesus how He was so patient, and generous with His time.  Never eager to set others aside so He could “get back to His business”, but to genuinely concern Himself with their issues too.  I believe this is what it means to bear one another’s burdens:
Galatians 6:2 “Bear one another’s burdens, and thereby fulfill the law of Christ”