Tutorial 1: Visitor enabling for IFF Pencil 2
Requirements are One of the Following:IFF Pencil 2(http://iffedit2.simprograms.com), Script Station(Availiable for download at http://www.yuppiesim.com), or MenuEditor(I already said the location)

Steps....
Part 1:Visitor Enable. This is tuitorial is done with MenuEditor.
1)Open MenuEditor
2)Choose the iff File you want to edit
3)On the left Side under Flags you will see a Box that says 'Availiable to Visitors' unchecked.
4)Check the box then save
5)Start Sims and Enjoy your Visitor Enabled object.

If Someone wants to explain how to do it with Script Station or IFF Pencil 2, Feel free to do so. 

Tutorial 2:Visitor enabling Objects with Script Station

Requirements:Script Station(duh), and An Object File outside a FAR file.

Part 1:Visitor Enabling
1)Open Script Station
2)Open the Iff file you want to edit
3)Now, you see a bunch of BHAVs and stuff like that. You can see that SS is more Advanced than MenuEditor. You want to look at the section that says Interaction Sections.
4)Now, There can sometimes be more than One file here. Choose the One that you want to visitor enable (A Lovebed would be Bed - Double - Heart tree table)
5)There are a bunch of Options here. Same as MenuEditor. Choose the option you want to Visitor enable and check the box that says 'Availiable to Visitors
6)Save, but if you try to check anything else after You've saved... It'll crash.
7)Start Sims and Enjoy your new Visitor Enabled Object.

Tutorial 3:Visitor Enabling Objects for IFF Pencil 2
Part 1:Visitor Enabling
1)Open IFF Pencil 2
2)Open the IFF file you want to edit.
3)Click on TTAB.
4)Now, you double click on the Tree Table you want to Edit.
5)More options now, but now you can enable objects to be used by pets (UL). Choose the actions you want to visitor enable and check the 'Availiable to Visitors' Checkbox for each action.
6)Save then Quit
7)Start Sims and Enjoy your Visitor enabled object.

One more thing. SS and IFF Pencil 2 are very powerful programs, and they can be used to modify globals and hack objects. So be careful and don't attempt to edit anything unless you know EXACTLY what you are doing.