Assalamu Alaikum warahmatullahi t3ala wa barakatuhu,
Some advice for myself first, then you. May ALLAH t3ala give us all the tawfeeq to act upon this advice, aameen thumma aameen
To concentrate in salah you have to remind yourself who your standing in front of. Is he just some random person? Is he a friend? How would you approach a person of big status like a king? Remember the one who you are approaching is your creator; The king of ALL kings! When you think about his status, and that hes capable of anything and everything.
Also, Ulema always advice not to rush right to salah.
Make ablution about 10-5 minutes before salah time, sit down on the prayer mat, and do zikr from your heart, ponder over who you are about to talk to. You have to take your heart and mind out of your daily activites, and bring them towards your salah. Salah is the only ibaadah in islam in which you do takbeer (raising your hands to your shoulders/earlobes, and saying ALLAHU akbar), and you know why?Raising your hand to your shoulders is a sign that you are leaving everything, the world, anything that concerns it, all thoughts behind you (behind your hands),and now you are approaching ALLAH t3ala. InshaALLAH t3ala when you do this, your brain will get the time to take itself out of the worldy activities, and concentrate in salah.