Why did Lavan (who was in no way on a par with his sister and daughter) run to greet Ya'akov?
Rashi: Lavan ran when he heard who had arrived. He figured that if the family's servant had arrived with ten camels laden with 'goodies', imagine what the master must have brought with him! So he ran out to see what was in it for him. 1
Seforno: He ran when he heard how Ya'akov had removed the stone from the well single-handed.
Targum Yonasan: He ran because he was intrigued by his nephew's strength and piety, and by all that happened to him - the episode of the B'rachos, the revelation in Beis-El, how he had rolled the stone off the well and how the well began to flow and rose to meet him.
It is truly remarkable; almost a hundred years had passed, but Lavan's greed had not abated one iota! (EC). Tosfos ha'Shalem (6): Lavan wanted to steal from him.
Yakov kissed (Menasheh and Efrayim) and then embraced them (Bereishis 48:10). Why did Lavan embrace and then kiss?
Rashi: When he saw no camels, he thought that perhaps he had brought gold coins with him, which were hidden somewhere on his body, so he embraced him; when he found nothing, he figured that he must have hidden some jewels in his mouth, 1 so he kissed him.
Does one hide jewels in his mouth? This is lunacy! This shows that bad Midos (e.g. lust for money) can bring to lunacy. (Ohr Yechezkel Darchei ha'Avodah p.184)
What exactly did Ya'akov tell Lavan?
Rashi: He told him that he was running away from his brother and related what had happened on the way - to explain why he came empty-handed. 1
Rashbam: That his parents had sent him, to be with his family.
Seforno: He informed him that he had come, not for Parnasah, but to escape his brother, and that he was following his parents' instructions.
Bechor Shor: He told him about getting the Brachos and Bechorah, so Lavan will want to give his daughter to him.
רש"י: ויחבק...שמא זהובים הביא והנם בחיקו. וינשק...שמא מרגליות הביא והם בפיו: וכי בחיבוק ונישוק הוא יגלה את הממון שהחביא יעקב?
גור אריה: הכוונה שלבן חשב שאולי יעקב מסתיר ממון ואם הוא יחבק אותו הוא יתדבק בו לגמרי ואז ימשוך את אהבתו אליו, ולא יעלים יעקב ממנו. והוסיף לבן לנשקו כי הפה נסתר יותר וע"י הנשיקה הוא רצה למשוך את פנימיותו באהבה יתירה ולהוציא אפי' דבר שנסתר לגמרי.
רש"י: ויחבק...שמא זהובים הביא וכו': מנין שכך חשב לבן?
גור אריה: אין דרכו של רשע לחזר על אורחים [ועל כרחך שהייתה דעתו להרוויח ממון].