Assuming he's familiar with the rubrics but hasn't memorized the prayers yet, these are the ones he should know by heart.

1. The prayers at the foot of the Altar
2. The start of the prayer as he walks up the altar
3. The end of the prayer as he walks towards the epistle side
4. The Gloria Patri (he will be facing the tabernacle so he can't read the missal)
5. The Kyrie series (not on missal card)
6. For the Gloria, he can read the card but he will be making head bows
7. Oremus
8. Per Dominum nostrum...
9. Per eundem Dominum...
10. Qui vivis et regnas...
11. Qui tecum vivit et regnas...
12. Per Evangelica dicta, deleantur nostra delicta
13. For the Credo, can read the card but he will be making head bows
14. Offérimus tibi, Dómine, cálicem salutáris, tuam deprecántes cleméntiam: ut in conspéctu divínæ maiestátis tuæ, pro nostra et totíus mundi salute, cum odóre suavitátis ascéndat. Amen. (this is on the altar card, but he should be looking at the crucifix while saying the words).
15. Veni, sanctificátor omnípotens ætérne Deus: Benedicit Oblata, prosequendo: et bene ✠ dic hoc sacrifícium, tuo sancto nómini præparátum. (here he will be making movements which might make it extra difficult to read the altar card)
16. Oráte, fratres: ut meum ac vestrum sacrifícium acceptábile fiat apud Deum Patrem omnipoténtem.
17. Grátias agámus Dómino, Deo nostro.
18. Sanctus, Sanctus, Sanctus Dóminus, Deus Sábaoth. Pleni sunt coeli et terra glória tua. Hosánna in excélsis. Benedíctus, qui venit in nómine Dómini. Hosánna in excélsis.
19. Te igitur, clementíssime Pater, per Iesum Christum, Fílium tuum, Dóminum nostrum, súpplices rogámus, ac pétimus,
20. The mass intention
21. The feast day of any saint mentioned in the canon, he'll need to bow his head when he reads his name.
22. Iesu Christi
23. omnipoténtem
24. tibi grátias agens
25. Súpplices te rogámus, omnípotens Deus: iube hæc perférri per manus sancti Angeli tui in sublíme altáre tuum, in conspéctu divínæ maiestátis tuæ: ut, quotquot
26. Dómine, non sum dignus,: ut intres sub tectum meum: sed tantum dic verbo, et sanábitur ánima mea
27. ecce agnus dei ecce qui tollit peccata mundi
28. Remember, "you" not "us" in the absolution
29. Ite, Missa est. (or others)
30. Benedícat vos omnípotens Deus, Pater, et Fílius, ✠ et Spíritus Sanctus.
31. Leonine Prayers (many times his altar server will have a card)
32. The blessing for the altar server