1. Producing ح like ه, and ع like ء
English has neither ح nor ع. Practise the pairs أَهْ / أَحْ and أَءْ / أَعْ. See Makharij.
2. Reading heavy letters as light
ص ض ط ظ ق غ خ are always heavy. صِرَاط read with a light س changes the word. Practise with the tongue raised towards the palate.
3. Adding a vowel after a sukoon
قَدْ becomes قَدَ. Practise stopping the letter cleanly, and note that qalqalah letters bounce but do not take a vowel. See Qalqalah.
4. Cutting ghunnah short
إِنَّ and ثُمَّ need about two counts of nasal sound. See Ghunnah.
5. Over-lengthening natural madd
قَالَ is two counts, not four. Verse endings are the usual place this creeps in. See Madd.
6. Treating ikhfa as izhar
مِن شَرِّ read with a clear noon. The noon should be hidden with ghunnah. See Ikhfa.
7. Pronouncing ث as س and ذ as ز
The tongue must touch the edge of the upper front teeth for ث and ذ.
8. Ignoring stopping changes
Stopping on أَحَدٌ as ahadun instead of ahad, or on ة as ت. See Stopping Rules.
9. Inconsistent madd at stops
Reading the temporary madd as two counts on one verse and six on the next. Choose one and keep it.
10. Rushing
Most errors appear at speed. Slow down until each rule is automatic, then build pace.
Fixing them
Record yourself reading one short surah, listen for these ten, then recite it to a teacher. Our Quran with Tajweed course tracks exactly which errors recur.