tipperary has a good sugestion there... got to planning dept and look at current planning apps or ones already granted..... (any neighbours had something similar done?... their planning files should be available to VIEW... no photocopies allowed but you can sketch/ take notes)
Use local papers to advertise... cheaper if you do mess up.... you dont need to use Irish Times.... at aprox €250 for advert.... when local papers may do at €60... so if there is a mistake... the planning dept will say what is missing and you can re advertise.... phone the planning department and find which paper for advertising will be acctable in your area....
In Cork, Limerick & Waterford it is 6 copies of everything.... not sure if this is standard... guessing it is... Full dimensioned drawings of existing dwelling needs to be submitted to scale 1/100 all dimensioned in metric along with proposed drawings (plans, Elevations & sections)...
Getting the wording of advert & site notice is vital, ask the planning department for their help. ie A Single Story Side Extension to existing dwellinghouse and A Single Story Extension to Side of existing dwellinghouse are two completly different things, one is attached to dwelling, the other is to the side of dwelling indicating it may not be attached. This is where the Irish Times or equivelent paper advertising will be expensive for your purpose as any minor misreading will delay application by 4 wks in system and result in resubmitting and readvertising.
And note.... 40 m2 (aprox 400ft2) extension to rear of existing dwelling is exempt as long as there is a remaining 25m2 of open gardan space remaining. the planning Dept will give you advice on this.