The simplest things you can do to protect yourself while away are:

Shelter Troops.
This prevents any troops ending up in the Infirmary costing you rss to heal.
Never have more resources than your Vault can hold. Use The Boat to convert rss into your Backpack
Never have too much gold. This also ties in with The Boat.
Use the The Bank to keep your gold/resources as low as possible.
Rally empty castles. Look for an unguilded castle around 400 miles (1 hour) away.
You might want to scout it first. Once you've found one you like, bookmark it.
Setting up an 8 hour rally on it actually gives you 10 hours of time offline before your troops return to your castle.
Until they are back, your troops cannot be attacked
Reinforce or garisson a shielded castle (assuming you know the length of their shield) with your troops AND your leader.
You can always recall them if you need access.
If it's a pinch where you're going to be gone for longer than any shields will be up, look for a remote area 400+ miles away where there are no hives nearby, ideally no guilded castles either.
Set up a camp near a known empty castle.
Your odds of your camp being randomly hit is lower than your castle being hit if you're in a hive.
When farmers come, they look for 3 things mainly:
Gold - Can't be held in the vault, so all of it is available to raid
Excess resources - If you have more than your vault can hold, they will know it.
Defense troops - What is the risk/reward for an attack.
If there is little to gain, they will look for someone else.
If they are just spiteful bastards, they might burn down your walls, but gain little out of it other than knowing they are pricks.
So mainly all you need to do is shelter Shelter and SHELTER!!!

If they are a lot bigger than you, bubble up and wait it out.
If they are distracted and you have the troops, try to see if they are burning castles or sending probes (a troop that doesn't return).
If they are sending out most of their forces, many times, you can send in your army and take everything they stole.
Just be sure to notice the castle levels and scout.
Tier 2 troops don't do well against Tier 3 traps and soldiers.
If you don't care about your castle walls, there is always the Gnat Attack to annoy them.
Shelter all but a handful of your lowest level troops (having a small group of Tier 1s is the cheapest).
Send them 1 troop at a time as fast as you can.
if they attack you, send your troops to the closest resource tile, then recall them after the attack is over to resume.
Adding scouts to keep your gold near 0 also helps to clutter their message feed so they have to try to find their own scouting reports and battle results.
Combining the Gnat Attack with a Backdoor Attack confuses the enemy, so they aren't certain what to do, and many times will leave them without the proper defense or offense to handle what is coming.
The goal is to make it more expensive or frustrating to "mine rss" from the guild than what they gain.
Always check who else is around. If they are farming over their heads, a rally might work, but it's always best to find the largest online person to start it so that we can send the most troops.