Improving makefile to look into subdirectories - c++

Question

Some time ago I had a need to create a makefile to work with a lot of small test projects that I was making. The whole scope was to simply compile all .cpp files in its directory, and to sort out object files and dependencies. However, one of those projects finally grew much enough that I'm in need of creating custom subfolders to keep all the code organized.
The problem is that I don't know all that much about makefiles, and the one I made is composed of bits and scraps I found around the internet. I was wondering how would I modify this code to be able to include files from different folders. What I have now is this:
SHELL=/bin/bash
CC=g++
EXECUTABLE=ruletheskies
CFLAGS=-std=c++0x -Wall -pedantic #-I/usr/include/boost_1_51_0/
LDFLAGS=-L./
LIBRARIES=-ljson_linux-gcc-4.6_libmt -lbprinter
WINLIBRARIES=-ljson_mingw_libmt -lbprinter_mingw
WINDEFINES=-DWINVER=0x0400 -D__WIN95__ -D__GNUWIN32__ -DSTRICT -DHAVE_W32API_H -D__WXMSW__ -D__WINDOWS__
WINLDFLAGS=-I./ # $(shell find /usr/include/ -maxdepth 1 -type d | sed 's/^/-I/g') #-L/usr/lib/ -I/usr/include/
WINBASELIBRARIES=-lodbc32 -lwsock32 -lwinspool -lwinmm -lshell32 -lcomctl32 -lctl3d32 -lodbc32 -ladvapi32 -lodbc32 -lwsock32 -lopengl32 -lglu32 -lole32 -loleaut32 -luuid
WINSTATIC=-static-libstdc++ -static-libgcc
WINOPTIONS=--verbose
SOURCES := $(wildcard *.cpp)
HEADERS := $(wildcard *.h)
OBJECTSFOLDER=objects
OBJECTS=$(addprefix $(OBJECTSFOLDER)/, $(SOURCES:.cpp=.o))
DEPFOLDER=dependencies
df=$(DEPFOLDER)/$(*F)
odf=$(OBJECTSFOLDER)/$(*F)
EXEFOLDER=bin
.PHONY : all
# Brute force compiling statement for simple compilation and no .o residual files
all: $(EXEFOLDER)
$(CC) $(CFLAGS) $(LDFLAGS) *.cpp $(LIBRARIES) -o $(EXEFOLDER)/$(EXECUTABLE)
.PHONY: debug
# Compiles using object files in OBJECTSFOLDER, only modified stuff
debug: folders $(SOURCES) $(EXEFOLDER)/$(EXECUTABLE)
.PHONY: windows
# cross-compilation: mingw has to be selected, adds libraries for windows, brute force
windows: $(EXEFOLDER)
$(CC) $(CFLAGS) $(WINDEFINES) $(WINSTATIC) $(LDFLAGS) $(WINLDFLAGS) *.cpp $(LIBRARIES) $(WINLIBRARIES) $(WINBASELIBRARIES) -o $(EXEFOLDER)/$(EXECUTABLE).exe $(WINOPTIONS)
# Final linking of the executable
$(EXEFOLDER)/$(EXECUTABLE): $(OBJECTS)
$(CC) $(LDFLAGS) $(OBJECTS) $(LIBRARIES) -o $#
# Creation of object files
# ( Actual compilation is only last instruction, the rest is creating dependency header rules )
$(OBJECTSFOLDER)/%.o: %.cpp
#$(CC) -MMD -c $(CFLAGS) -o $# $<
#cp $(odf).d $(df).P; \
sed -e 's/#.*//' -e 's/^[^:]*: *//' -e 's/ *\\$$//' \
-e '/^$$/ d' -e 's/$$/ :/' < $(odf).d >> $(df).P; \
rm -f $(odf).d
$(CC) -c $(CFLAGS) $< -o $#
-include $(DEPFOLDER)/*.P
# Creation of folders
.PHONY : folders
folders: $(OBJECTSFOLDER) $(DEPFOLDER) $(EXEFOLDER)
$(OBJECTSFOLDER):
mkdir $#
$(DEPFOLDER):
mkdir $#
$(EXEFOLDER):
mkdir $#
# Cleanup of object files
# ( .PHONY is to avoid calling the rule in case a file named clean exists )
.PHONY : clean
clean:
rm -rf $(OBJECTSFOLDER)
rm -rf $(DEPFOLDER)
I imagine I'll have to modify the SOURCES := $(wildcard *.cpp) line, but how would I include the subdirectories I have to look into, whatever they may be? I'm planning to keep corresponding header and source files together, if that simplifies things.