How can a person know if his Lord is pleased with him?

Praise be to Allah.  

Among the signs that the Lord is pleased with His slave is that He guides him to do good deeds and avoid haraam things. This is confirmed by the words of Allah: 

{وَالَّذِينَ اهْتَدَوْا زَادَهُمْ هُدًى وَآتَاهُمْ تَقْوَاهُمْ}  

'Translation' {While as for those who accept guidance, He increases their guidance and bestows on them their piety} [Muhammad:17]. 

{وَالَّذِينَ جَاهَدُوا فِينَا لَنَهْدِيَنَّهُمْ سُبُلَنَا}  

'Translation' {As for those who strive hard in Us (Our Cause), We will surely guide them to Our paths (i.e. Allah’s religion- Islamic Monotheism)} [al-'Ankaboot from the verse:69] 

But if a person is hindered from doing good deeds and avoiding haraam things -we seek refuge with Allah- then that is a sign that Allah is not pleased with him. 

Allah has also explained in His Book that the sign of His being pleased with His slave and of His guidance is that He opens his heart to true guidance and true faith. And the sign of misguidance and being far from the Straight Path is distress and constriction in the heart. Allah says: 

{فَمَن يُرِدِ اللَّـهُ أَن يَهْدِيَهُ يَشْرَحْ صَدْرَهُ لِلْإِسْلَامِ ۖ وَمَن يُرِدْ أَن يُضِلَّهُ يَجْعَلْ صَدْرَهُ ضَيِّقًا حَرَجًا كَأَنَّمَا يَصَّعَّدُ فِي السَّمَاءِ ۚ كَذَٰلِكَ يَجْعَلُ اللَّـهُ الرِّجْسَ عَلَى الَّذِينَ لَا يُؤْمِنُونَ}

'Translation' {And whomsoever Allah wills to guide, He opens his breast to Islam; and whomsoever He wills to send astray, He makes his breast closed and constricted, as if he is climbing up to the sky. Thus Allah puts the wrath on those who believe not} [al-An'aam:125]. 

Ibn 'Abbaas said, commenting on this verse: {And whomsoever Allah wills to guide}: He opens his heart to Tawheed and belief therein" (Tafseer Ibn Katheer, [2/175]).   

Another sign of Allah's love for His slave and His being pleased with him is that He makes him beloved to His slaves. Al-Bukhaari [3209] and Muslim [2637] narrated from Abu Hurayrah that the Prophet (peace and blessings of Allah be upon him) said: «When Allah loves a person, He calls out to Jibreel: "Allah loves So and so", so Jibreel loves him. Then Jibreel calls out to the people of heaven, "Allah loves So and so, so love him". So the people of heaven love him and he finds acceptance on earth» .” 

Al-Nawawi said: "«and he finds acceptance on earth» means that people love him and are pleased to see him, so their hearts incline towards him. It says in another report: «and he finds love on earth»". 

And Allah knows best.