I would like to post some of my efforts at scanning Aeneid II for comment, but am not sure about the symbols used on the board.
It seems that - is used to represent a spondee, u a dactyl, and | a foot. How does one represent ellided words and caesuras?
gratias ago
Nigel
Well, most people posting scansions here seem to use a system similar to this: as a substitute for real macrons and breves, “-” marks a long syllable, and “u” marks a short. So a dactyl would be " - u u " and a spondee " - - ". I think I have seen // used for caesura. As for elision, I guess you can mark it with parenteses in the accompanying text. Something like this would work, I think:
If you want to ensure that the scanning lines up with the text, I suppose you can make use of the Code tag, but it is often tricky to get it right, so don’t bother with it unless you really want to:
- uu |- u u|- // u u|- - |- u u |- -
ostia dives opum studiisqu(e) asperrima belli;
You can also mark the scansion directly on the vowels. (Note that the macrons and breves in that case do not signify vowel length, but instead syllable length; for example, you would mark the “u” in “opum” with macron, because the syllable is long by position, even though the vowel itself is short.)
ōstĭă | dīvĕs ŏ|pūm // stŭdĭ|īsqu(e) ās|pērrĭmă | bēllī
Thanks for your reply. Here is my attempt at scanning lines 355 to 360 of Aeneid II. I seem to be finding a large number of spondees: am I doing something wrong or could this be because it is such a sombre passage that Virgil is using them for emphasis? Never though I'd say this, but I find scanning Attic Greek much easier! I apologise that the scansion marks and text don't align properly - have tried several times to get them right!
- u u| - u u | - u u |- - | - u u| - - |
sic animis iuvenum furor additus. inde, lupi ceu
- - |- - | - - |- - | - u u | - u u|
raptores atr(a) in nebula quos improba ventris
- - |- -| - u u | - -|- u u|- -|
exegit caecos rabies catulique relicti
- -| - -| - - | - -| - u u| - u u|
faucibus exspectant siccis, per tela, per hostes
- -| - -| - - | -_ u u | - u u |- u u
vadimus haud dubiam in mortem mediaeque tenemus
- u u|- u u|- -|- -| - u u| - -|
urbis iter; nox atra cava circumvolat umbra.
Told ya. 
Seriously, it is much easier if you compose your message in an editor that lets you use a monospaced font, such as Courier. When it looks good there, you can then copy the text into your browser.
I’d be delighted to help you with your scansions (there are a few errors), but to help you in the best way, it would be very helpful for me if you could clarify some things. Your first line went like this:
The problem here is that there are more syllables in the text than there are marks in your scansion, and since, as you noted, the scansion does not line up with the text, it is difficult for me to know what you intended. Anyhow, the correct scansion should be
- u u|- u u|- u u |- u u | - u u|- - |
sic animis iuvenum furor additus. inde, lupi ceu
(That is, short ĭ in additus.)
As for the other lines, note that a hexameter never, ever ends with a dactyl. So if you end up with that, you should probably reconsider that scansion. Another thing you should watch out for is syllables that are long by position. For example, without looking anything up, you can instantly see that the first syllable of “ventris” is long: the ‘e’ is followed by two consonants, ‘nt’, and so it must count as a long syllable.
I’ll let you have another try before I correct the rest of the lines.
Thanks again for your help - I've tried composing this in wordpad using courier, let's see if it helps.
Next attempt:
- u u|- u u| - u u | - u u | - u u|- - |
sic animis iuvenum furor additus. inde, lupi ceu
- -| - - | - u u|- -| - u u |- - |
raptores atr(a) in nebula quos improba ventris
- -| - -| - u u|- u u|- u u|- -|
exegit caecos rabies catulique relicti
- u u| - -| - -| - -| - u u | - -|
faucibus exspectant siccis, per tela, per hostes
- u u| - u u|- u u| - u u|- u u|- u|
vadimus haud dubiam in mortem mediaeque tenemus
- u u|- u u| - -|- -| - u u| - -|
urbis iter; nox atra cava circumvolat umbra.
Hi! The scansions look good, much better than the first try. Only the last two need corrections:
The first syllable of “mortem” is long by position. You have also missed an elision in this line; it might not be obvious at first glance… 
In the last verse, note that “x” counts as two consonants, so “nox”, too, is long by position. Of course, this means that some other parts of your scansion is wrong as well.
How is this now?
-u u | - u u| - - | - u u|- u u|- u|
vadimus haud dubia(m) in mortem mediaeque tenemus
- u u|- - | - u u|- - |- u u|- - |
urbis iter; nox atra cava circumvolat umbra.
Looks good to me!
tibi gratias ago
Nigel
I’ll try some more tomorrow.
I have scanned a few more lines of the Aeneid for comments, please:
- -| - -|- - |- -| - u u| - -|
quis clade(m) illius noctis, quis funera fando
- u u| - - |- u u|- -| - u u|- - |
explicet aut possit lacrimis aequare labores?
- - |- u u|- -| - u u|- u u| - -|
urbs antiqua ruit multos dominata per annos;
- u u| - u u|- -| - u u|- uu |- u|
plurima perque vias sternuntur inertia passim
- u u| - u u|- -| - u u|- u u|- u|
corpora perque domos et relligiosa deorum
- u u| - -|- -| - -| - u u |- -|
limina. Nec soli poenas dant sanguine Teucri;
- u u|- -| - u u| - - |- uu| - -|
quonda(m) etiam victis redit in praecordia virtus
- -|- u u|- u u|- -| - u u|- u|
victoresque cadunt Danai. Crudelis ubique
- u u|- u u|- - | - u u| - u u|- -|
luctus, ubique pavor et plurima mortis imago.
They are all correct, as far as I can see.
Thank you again for all your help (and very rapid response!)