If you have read all my posts in this topic so far, you should by now be able to read simple music in both treble and bass clefs. However, there is more to performance than merely reproducing the correct pitch for the correct duration. There is also the question of how you play the notes. I have already covered the issue of dynamics, but there is another, equally important area which you must master to achieve a good musical performance (or a good musical score), and that is articulation.
Articulation marks indicate the characteristics of particular notes (or chords) and how you should produce them. They are generally concerned with the attack and/or sustain of the notes, and the transition between consecutive notes. Examples include how much emphasis to apply to the notes and whether to play them short or long. One of the reasons we use articulation marks is because otherwise the notation is imprecise, and doesn't give us sufficient information into the intended nuances of the music.
Note that all the articulation marks are generally placed above or below the note-head (in the nearest space), on the opposite side to the stem. Just as with most of the aspects of notation we have encountered so far, the definitions for these marks has varied throughout history, and they are all open to interpretation. (The following represents the most common definitions, applicable to most music you will encounter).
Normally, without any articulation marks, a passage of music might look something like this:

In a case like this, the notes should be played detached, separate from each other. Each note has a definite start and a definite stop, and there is a (very small) gap between each note. On bowed string instruments, this is called detaché, and means all the notes are played with a different bow stroke (alternating between up-bows and down-bows). With wind instruments, this is called tonguing, because you generally use your tongue to start and stop each note.
To indicate a more flowing, continuous articulation, we use slurs, like this:

Here, the first note is played normally, as above, but the notes that follow it (that are contained within the slur) are not articulated separately. - They are played legato with no noticeable break between the notes. That is, the notes are joined smoothly together without them having as much individual attack, - there is not so much of a definite start or stop to each. On bowed string instruments the notes are all taken in the same bow stroke. On wind instruments, they are played in the same breath, without tonguing each one individually. Slurs can vary in length from only two notes to whole bars, or even more. In keyboard music, the slurred notes sometimes overlap very slightly, so the start of one comes fractionally before you take your finger of the first note. Obviously you can't have too long slurs (this also depends on the speed of the music) otherwise the player will run out of bow, or run out of breath. Note that slurs look like ties, but slurs are generally not placed between two consecutive notes on the same pitch (because they need to be articulated separately). It rarely makes sense to write slurs in drum parts (including timpani).
In addition to the above ways of playing, there are other marks that can further define the articulation:
Staccato
This is indicated by a dot above or below the note-head:

These notes are played shorter than their normal value. (And detached from the other notes). The notes are therefore played abruptly, with silence making up the reminder of the normal note-value. The actual degree of staccato can vary, but usually the notes are meant to be played roughly half their normal value (so staccato crotchets (quarter notes) result in quavers (eighth notes) or smaller). Obviously it doesn't generally make much sense to put a staccato over a note longer than a crotchet (quarter note), although sometimes this is encountered (particularly in unusual time-signatures and/or very fast music).
Tenuto
This is indicated by a short horizontal line above or below the note-head:

These notes are meant to be fully sustained. They need to be held for their full value, and sometimes even exceed it slightly.
Accents
These are indicated with small horizontal hairpins (>) above or below the note-head:

These notes need emphasis and more force than usual. Usually this means the note (or chord) is stronger and should be played slightly louder and stressed more than the other notes.
Vertical Accents
These are similarly to regular accents, but with a vertical hairpin (^ or v):

This generally indicates an even stronger emphasis than the regular accent described above. - Even more force is needed for these notes (or chords), and sometimes it also implies some degree of staccato too (as detailed above). These are sometimes referred to as a type of Sforzando or Marcato, but exact definitions vary quite a bit. Note that the biggest part of the chevron is closest to the note-head. Not to be confused with an up-bow marking for bowed stringed instruments.
Staccatissimo
These look like small, filled-in arrow-shaped wedges:

This means the note should be played even shorter than a regular staccato (as described above). - Generally the notes (or chords) should be as short as possible, and possibly with a slight accent too (as described above). Note that the smallest part of the wedge is closest to the note-head.
Sometimes, two or more of these articulation marks can be combined on a single note or chord. - The result, unsurprisingly, is generally a combination of both effects. In notation, you should write a staccato dot first closest to the note-head, then a tenuto line after this, then any slurs or ties, then finally other accents in order of intensity, from weakest to strongest.
Note also that when any particular articulation mark is to be applied to a long section of music, instead of writing the articulation mark over every note, you sometimes write the word instead. For example, a piece marked staccato is to be played as though there was a dot above (or below) each note.


















