I just finished my grade 8 (passed with merit) and aural was always the biggest problem for me too. I found that it was helpful to listen to the aural practise cassettes, practise sight singing any musical notation you can find and to practise playing cadences and intervals so that you learn to recognise them. It also helped to make revision notes for the last part of the aural test which is to describe a piece of music.
Write a list of categorised vocab that would help you in describing an extract of music in terms of:
style (e.g. animato, scherzo, cantabile, expressivo)
texture (e.g.contrapuntal, harmonic)
rhythm (e.g. 2s against 3s, dotted, syncopated)
tonality (e.g. major/minor, atonal, chromatic)
form (binary AB, ternary ABA, rondo ABACA)
Also look out for things you can say about phrasing (whether it's long or short), imitation, theme and variation and cadences or whether it's a dance (e.g. fugue, minuet, waltz)...etc.
As for the characteristics of music from the different periods..i hope this helps.
BAROQUE: Imitation, ornaments, many cadential points, contrapuntal (fugue). [Possible composers are: handel, bach, vivaldi, purcell, scarlatti]
CLASSICAL: Alberti bass, harmonic, ascending and descending scale passages, sonata form, structural phrases with cadence at the end of each phrase. [Mozart, beethoven, hadyn]
ROMANTIC: Expressive, waltz (identified by the 3/4 time bass accompaniment), shifting between major and minor frequently, use of triplets, rich texture and harmony. [Tchaikovsky, chopin, schubert, brahms (beethoven)]
MODERN/20TH CENTURY: Atonal, impressionistic, mix of high and low register, narrative (programme music). [Schoenberg, debussy, ravel, strauss, shostakovich]
These were basically all the notes that i made. But if anyone notices any mistakes please correct me!
Hope this has helped