I conducted this piece with the Royal Danish Ballet in march this year, in the Balanchine ballet aptly named "Serenade". I added explanations, so as to give you an idea of how I mark my scores.
As you can see in these images, I have many different little symbols or techniques. What I've used in this specific score, is just a small sample of my private 'library' of symbols.
(click on the images to enlarge)
Each conductor has his own semantics, and looking through a colleague's score is very interesting for that reason. This act of marking a specific detail in the score, is both useful for directing my focus to specific elements during rehearsal or performance and also serves to somehow mark it in my brain.
Once I write "B.Cl." with blue pencil at a Bassclarinet entry, it's there in my brain as well.
The markings are always relatively big, making them easily visible from a distance (so I don't bend down over the score too much) and also includes changes in tempo and anything else I find interesting, important or unusual. For example:
I usually write very large "Rit." or "Acc." sometimes followed by an appropriate dotted line for the multi-measure tempo-changes (ritardando/accelerando).
Just like a lot of conductors and repetiteurs, I use the ubiqiutous ~ for smaller, local stretches in tempo.
For a sudden change in tempo, I use ↑ and ↓ for "uptempo" or "downtempo".
For an exact doubling of the tempo, I use ↑↑
I mark local bar-structures in my scores a lot; 8-bar period, vertical line, 4-bar period, vertical line, 4-bar period and so on. Many conductors only mark the much larger structures that way, or not at all.
Some even use a variety of colorful pencils for this purpose, but I don't know where that 'school' originated - to me it looks completely weird with green, orange, purple lines going down the score on every page, but...chacun son goût.
Now, I also have a long list of abbreviations for the specific instruments/soloists/singers, and this is as varied among conductors as it is among publishers and composers. Over the years, I have boiled it down to this eclectic mix - which is different from what I write in my compositions by the way.
For voice: if there's just a single one, I simply write "V", but for specific parts in an opera, I invent my own abbreviations; "K'in" for Kaiserin or "Lep" for Leporello for example.
For the orchestra instruments, I use the following:
Fl. = flute / Picc. = Piccolo /A.Fl. =Altoflute
Ob. = Oboe / C.a. = Cor Anglais
Cl. = clarinet / B.Cl = Bassclarinet
Fg. = Bassoon (which is a 'fagot' in danish) / C.Fg. = Doublebassbassoon.
Cor. = Horn
Trp. or sometimes just Tp = Trumpet
Tb. = Trombone /B.Tb. = Basstrombone
Tu. = Tuba
Pk. = Timpani (pauke)
Sometimes I frame a whole section at a time (or large portions) and use the following:
W.W. = Woodwinds
Brass = well...u can figure it out
Perc. = Percussion
Str. = Strings
For the individual string sections, I write
I = 1st violins
II = 2nd violins
Vla = Violas
Vlc = Cellos
Cb. = Basses
Hp. = Harp
Pno. = Piano
Cel. = Celeste
For certain standard percussion instruments, I have my own little drawings that I use all the time (aren't they cute?):
I think that's it for now. When I have time, I'll try to scan a few more examples from my scores, so you can see how inconsistent I really am.
Todays little aperitif is from when I was a hornplayer in the Odense Symphony Orchestra. We were rehearsing the introduction of the Adagio of Bruckner's 7th - in which the hornsection plays an amazing chorale on the socalled Wagnertubas, a slightly difficult instrument to master.
Michail Jurowski was conducting, and he was not satisfied. He interrupted us with a frown saying;
"You know, there are quartets of excellent wagnertuba-players who travel around in Germany specialising in just this!" - meaning, if we didn't improve, he would have those guys flown in to replace us all.
Replied the oldest member of our section, the always drywitted Bruno: "And there are also quite excellent conductors in Germany who can conduct this symphony!"
We heard little more of complaints from Jurowski that week.