The good vision are from Allah and the evil dreams are from the satan. If one sees a dream which one does not like, one should spit on one's left side and seek the refuge of Allah from the satan; it will not do one any harm, and one should not disclose it to anyone and if one sees a good vision one should feel pleased but should not disclose it to anyone but whom one loves.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ الرُّؤْيَا الصَّالِحَةُ مِنَ اللَّهِ وَالرُّؤْيَا السَّوْءُ مِنَ الشَّيْطَانِ فَمَنْ رَأَى رُؤْيَا فَكَرِهَ مِنْهَا شَيْئًا فَلْيَنْفِثْ عَنْ يَسَارِهِ وَلْيَتَعَوَّذْ بِاللَّهِ مِنَ الشَّيْطَانِ لاَ تَضُرُّهُ وَلاَ يُخْبِرْ بِهَا أَحَدًا فَإِنْ رَأَى رُؤْيَا حَسَنَةً فَلْيُبْشِرْ وَلاَ يُخْبِرْ إِلاَّ مَنْ يُحِبُّ